Upgrading the National Car Assessment Program: Enhancing Vehicle Safety for a New Era

Department of Transportation

National Highway Traffic Safety Administration

[Docket No. NHTSA-2021-0002]

AGENCY:

National Highway Traffic Safety Administration (NHTSA), Department of Transportation (DOT).

ACTION:

Request for comments (RFC).

SUMMARY:

The National Car Assessment Program (NCAP), a cornerstone of vehicle safety assessment, is taking significant steps to better inform consumers and drive safety innovation. NHTSA’s NCAP currently provides crucial comparative safety information, empowering consumers to make informed vehicle purchasing decisions while motivating manufacturers to pursue continuous safety enhancements. Beyond the familiar star ratings for crash protection and rollover resistance, NCAP actively recommends advanced driver assistance systems (ADAS) technologies, highlighting vehicles equipped with systems that meet stringent NCAP performance benchmarks. This notice proposes substantial upgrades to the national car assessment program, primarily by introducing four cutting-edge ADAS technologies to the recommended list. These technologies include blind spot detection, blind spot intervention, lane keeping support, and pedestrian automatic emergency braking. Further updates and enhancements to NCAP are detailed in the Supplementary Information section below.

DATES:

To ensure your voice is heard, please submit comments no later than May 9, 2022.

ADDRESSES:

Please reference the docket number provided above and submit your comments through one of the following channels:

Federal eRulemaking Portal: https://www.regulations.gov. Follow the straightforward online instructions for comment submission.
Mail: Docket Management Facility, U.S. Department of Transportation, 1200 New Jersey Avenue SE, West Building Ground Floor, Room W12-140, Washington, DC 20590-0001.
Hand Delivery: 1200 New Jersey Avenue SE, West Building Ground Floor, Room W12-140, Washington, DC, accessible between 9 a.m. and 5 p.m. ET, Monday through Friday, excluding Federal Holidays.
Instructions: Comprehensive instructions for submitting comments can be found under the “Public Participation” heading in the SUPPLEMENTARY INFORMATION section of this document. It is important to note that all comments received will be publicly posted without modification at https://www.regulations.gov, including any personal information provided.
Privacy Act: The electronic format of all comments received in any of our dockets is searchable by the name of the individual submitting the comment (or the signing individual, if submitted on behalf of an organization). For a detailed review of DOT’s Privacy Act Statement, please refer to the Federal Register published on April 11, 2000 (65 FR 19477-78) or visit https://www.transportation.gov/privacy. For access to docket materials, background documents, and received comments, please visit https://www.regulations.gov or the physical address listed above and follow the online instructions.

FOR FURTHER INFORMATION CONTACT:

For technical inquiries, please contact Ms. Jennifer N. Dang, Division Chief, New Car Assessment Program, Office of Crashworthiness Standards (Telephone: 202-366-1810). For legal inquiries, please contact Ms. Sara R. Bennett, Office of Chief Counsel (Telephone: 202-366-2992). Written correspondence can be directed to either official at the National Highway Traffic Safety Administration, 1200 New Jersey Avenue SE, West Building, Washington, DC 20590-0001.

SUPPLEMENTARY INFORMATION:

This notice outlines proposed enhancements to the national car assessment program, including more rigorous test procedures and performance criteria for the four ADAS technologies currently recommended by NCAP. These updates aim to provide a more robust evaluation of their effectiveness in modern vehicles and to align with other leading consumer information programs. Furthermore, this notice explores the development of a comprehensive rating system for vehicles equipped with these ADAS technologies, seeking public comment on the optimal design of such a system. In accordance with the 2015 Fixing America’s Surface Transportation (FAST) Act, NHTSA is also considering integrating a crash avoidance rating onto a vehicle’s window sticker (Monroney label) at the point of sale, and is actively exploring effective implementation strategies, including a dynamic update process.

As part of a forward-thinking approach, NHTSA is proposing a phased “roadmap” for NCAP upgrades over the coming years, inviting public comment on this strategic framework. In a groundbreaking step, NCAP is considering expanding its scope to raise consumer awareness of safety technologies that promote safer driving choices. This initiative is particularly relevant for parents and caregivers selecting vehicles for new drivers or seeking enhanced rear seat safety features like hot car/heatstroke alerts. Finally, this RFC opens discussion on programmatic improvements to NCAP, aiming to optimize the program’s overall effectiveness. This comprehensive proposal, focusing on ADAS technologies and broader safety initiatives, is a significant step towards a more comprehensive safety strategy. It directly addresses the 2015 FAST Act directive and the recent mandates of Section 24213 of the November 2021 Bipartisan Infrastructure Law (Infrastructure Investment and Jobs Act), all geared towards enhancing road safety for vehicle occupants and vulnerable road users alike.

I. Executive Summary
II. Background
III. ADAS Performance Testing Program
A. Lane Keeping Technologies

Updating Lane Departure Warning (LDW)
a. Haptic Alerts
b. False Positive Tests
c. LDW Test Procedure Modifications
Adding Lane Keeping Support (LKS)
B. Blind Spot Detection Technologies
Adding Blind Spot Warning (BSW)
a. Additional Test Targets and/or Test Conditions
b. Test Procedure Harmonization
Adding Blind Spot Intervention (BSI)
C. Adding Pedestrian Automatic Emergency Braking (PAEB)
D. Updating Forward Collision Prevention Technologies
Forward Collision Warning (FCW)
Automatic Emergency Braking (AEB)
a. Dynamic Brake Support (DBS)
b. Crash Imminent Braking (CIB)
c. Current State of AEB Technology
d. NHTSA’s CIB Characterization Study
e. Updates to NCAP’s CIB Testing
f. Updates to NCAP’s DBS Testing
g. Updates to NCAP’s FCW Testing
h. Regenerative Braking
FCW and AEB Comments Received in Response to 2015 RFC Notice
a. Forward Collision Warning (FCW) Effective Time-to-Collision
b. False Positive Test Scenarios
c. Procedure Clarifications
d. Expand Testing
e. AEB Strikeable Target
IV. ADAS Rating System
A. Communicating ADAS Ratings to Consumers
Star Rating System
Medals Rating System
Points-Based Rating System
Incorporating Baseline Risk
B. ADAS Rating System Concepts
ADAS Test Procedure Structure and Nomenclature
Percentage of Test Conditions to Meet—Concept 1
Select Test Conditions to Meet—Concept 2
Weighting Test Conditions Based on Real-World Data—Concept 3
Overall Rating
V. Revising the Monroney Label (Window Sticker)
VI. Establishing a Roadmap for NCAP
VII. Adding Emerging Vehicle Technologies for Safe Driving Choices
A. Driver Monitoring Systems
B. Driver Distraction
C. Alcohol Detection
D. Seat Belt Interlocks
E. Intelligent Speed Assist
F. Rear Seat Child Reminder Assist
VIII. Revising the 5-Star Safety Rating System
A. Points-Based Ratings System Concept
B. Baseline Risk Concept
C. Half-Star Ratings
D. Decimal Ratings
E. Rollover Resistance Test
IX. Other Activities
A. Programmatic Challenges With Self-Reported Data
B. Website Updates
C. Database Changes
X. Economic Analysis
XI. Public Participation
XII. Appendices

I. Executive Summary

NHTSA’s National Car Assessment Program (NCAP) plays a pivotal role in the agency’s mission to minimize fatalities and injuries on U.S. roads. NCAP, alongside other NHTSA initiatives, has been instrumental in significantly reducing motor vehicle fatalities. In the decade preceding NCAP’s inception in 1978, annual fatalities surpassed 50,000. While this number decreased to 36,096 in 2019[1], with passenger vehicle occupant fatalities declining from 32,225 in 2000 to 22,215 in 2019[1], further progress is crucial, especially considering the increasing vehicle miles traveled (VMT) in the U.S. Pedestrian fatalities, however, have alarmingly risen by 33 percent from 2000 to 2019[2]. Recent statistical projections for the first half of 2021 reveal an estimated 20,160 traffic fatalities – the highest since 2006 and the largest half-year percentage increase in recorded history[3]. The second quarter of 2021 alone saw 11,225 fatalities, the highest since 1990 and the highest quarterly percentage change (+23.1 percent) ever recorded[3]. While VMT rebounded in the first half of 2021 following the pandemic-related dip of 2020, fatality rates also increased to 1.34 fatalities per 100 million VMT, up from 1.28 in 2020[3]. Emerging data suggests a link between increased fatality rates and risky behaviors such as unrestrained driving, impaired driving, and speeding[4]. Despite significant advancements in automotive safety over the past half-century, much more remains to be done.

This notice details how NCAP will bolster NHTSA’s mission through multifaceted initiatives and broad safety strategies aimed at enhancing vehicle safety for occupants and vulnerable road users, and promoting safer driving choices to further reduce injuries and fatalities. Aligned with the Department of Transportation’s National Roadway Safety Strategy, NCAP updates will prioritize safety features that protect individuals both inside and outside vehicles. This includes evaluating pedestrian protection systems, improving understanding of pedestrian impacts (especially concerning children), and promoting automatic emergency braking and lane keeping assistance for bicyclists and pedestrians. In a pioneering move, particularly relevant given the rise in risky driving behavior-related fatalities, this notice seeks public comment on how automakers can encourage consumers to adopt safety technologies that proactively prevent risky behaviors.

This notice proposes significant upgrades to the national car assessment program by incorporating four new crash avoidance technologies (ADAS), enhancing the stringency of tests for current NCAP-recommended ADAS, and, for the first time, extending NCAP’s scope to include safety for road users outside of vehicles. Finally, this document presents a roadmap outlining NHTSA’s phased plan for NCAP upgrades over the next decade.

These efforts are closely aligned with Section 24213 of the Bipartisan Infrastructure Law (Infrastructure Investment and Jobs Act)[5], enacted on November 15, 2021. Firstly, this RFC, once finalized, will fulfill Section 24213(a) by finalizing proceedings initiated in December 2015 regarding the addition of four technologies[6]. This finalization will close the 2015 proceeding, although data collected may inform future notices.

Secondly, this RFC partially fulfills Section 24213(b) by publishing a notice for public comment to establish consumer information means for advanced crash-avoidance technologies within a year of enactment. This includes: (1) methodology for technology inclusion, (2) manufacturer performance test criteria, (3) distinct rating systems per technology, and (4) overall vehicle rating updates. This RFC proposes four additional ADAS technologies[7], test criteria, and seeks input on developing a crash avoidance rating system. NHTSA justifies its technology choices and their alignment with NCAP inclusion criteria. By proposing technology additions and test criteria, NHTSA fulfills two of four requirements under Section 24213(b).

Section 24213(b) also mandates a notice within one year for consumer information on pedestrian, bicyclist, and vulnerable road user safety technologies, with similar requirements to the advanced crash avoidance notice. By proposing pedestrian automatic emergency braking (PAEB) and associated test criteria, NHTSA meets two of four requirements for vulnerable road user safety under Sec. 24213(b). The remaining requirements will be addressed upon proposing and finalizing a new crash avoidance technology rating system. The law also mandates reports to Congress on these plans, which NHTSA will fulfill promptly.

Thirdly, this RFC, upon finalization, fulfills Section 24213(c) by establishing a ten-year NCAP roadmap with five-year mid-term and long-term components, updated at least every four years based on agency interests and public input. This RFC’s roadmap fulfills this ten-year requirement, with initiatives planned for both the near and long term.

Fourthly, this RFC fulfills Section 24213(c) by making the roadmap available for public comment and considering public input before finalization. This aligns with current NCAP update practices. Section 24213(c) also requires identifying NCAP harmonization opportunities with third-party safety rating programs, which NHTSA is actively pursuing where feasible and appropriate, as noted throughout this RFC.

Fifthly, Section 24213(c) requires annual stakeholder engagement with diverse backgrounds to develop future roadmaps, which aligns with current NHTSA practice.

Components of the Notice

This notice comprises six key components:

Proposes adding four new ADAS technologies to NCAP and updating current NCAP test procedures.
Discusses the Agency’s plan to develop a new rating system for advanced driver assistance technologies.
Describes steps to list crash avoidance rating information on vehicle window stickers (Monroney labels) at the point of sale.
Describes a roadmap of the Agency’s plans to update NCAP in phases over the next ten years.
Requests comments on expanding NCAP to provide consumer information on safety technologies that could help people drive safer by preventing or limiting risky driving behavior.
Discusses NHTSA’s ideas for updating programmatic aspects of NCAP to improve the program overall.

Each of these aspects is detailed further below. Firstly, this notice details proposed upgrades to add four more ADAS technologies to those currently recommended by NHTSA via NCAP and highlighted on the NHTSA website. Since 2010, NCAP has recommended four ADAS technologies to vehicle purchasers, identifying vehicles offering systems meeting NCAP performance criteria[8]. Current recommended technologies include forward collision warning (FCW), lane departure warning (LDW), crash imminent braking (CIB), and dynamic brake support (DBS) (CIB and DBS are collectively referred to as “automatic emergency braking” (AEB)[9]). This notice proposes modifications (including increased stringency) to test procedures and performance criteria for LDW, CIB, DBS, and FCW to (1) enhance evaluation of their capabilities in current vehicle models, (2) reduce test burden, and (3) harmonize with other consumer information programs. This notice also proposes four additional ADAS technologies: blind spot detection, blind spot intervention, lane keeping support, and pedestrian automatic emergency braking.

These four new ADAS technologies are NCAP candidates because data indicates they meet NHTSA’s four prerequisites for inclusion: (1) addressing a safety need; (2) system designs to mitigate the problem; (3) safety benefit potential; and (4) objective performance test procedures. To address safety needs (criterion 1), the Agency prioritizes injuries and fatalities from “high-frequency and high-risk crash types,” offering the greatest potential benefit. NCAP, a non-regulatory consumer information program, does not calculate relative costs and benefits for inclusion. This notice details how each proposed ADAS technology meets these four prerequisites. As explained herein, these four new ADAS technologies are currently the only technologies believed to meet all four prerequisites for NCAP inclusion. Each technology has demonstrated the ability to mitigate high-frequency and high-risk crash types. With the pedestrian automatic emergency braking proposal, NCAP will expand, for the first time, to include safety for individuals outside of the vehicle.

Secondly, this notice discusses the Agency’s plan to develop a future rating system for new vehicles based on the availability and performance of all NCAP-recommended crash avoidance technologies. Currently, NCAP only recommends crash avoidance technologies and identifies vehicles offering technologies meeting NCAP performance criteria[10]. Unlike crashworthiness and rollover programs with combined ratings, the NCAP crash avoidance program lacks a rating system to differentiate ADAS technology performance. NHTSA aims to rectify this by developing an ADAS rating system to provide purchasers with improved data for comparison and shopping, and to incentivize enhanced vehicle performance. Accordingly, this document seeks public input on the optimal development of this rating system.

Thirdly, this notice announces NHTSA’s steps to list crash avoidance rating information on vehicle window stickers (Monroney labels) at the point of sale, as directed by the FAST Act. NHTSA seeks comments on Monroney label information ideas. Research is underway to maximize information effectiveness for purchasing decisions. A subsequent notice will propose the crash avoidance rating system and detail its usage. NHTSA will consider public comments alongside consumer research data to develop a revised label proposal. To further inform purchasing decisions, NHTSA plans to provide fuel economy and greenhouse gas rating information alongside NHTSA safety ratings, both at the point of sale and on the NHTSA website.

Fourthly, as part of a new NCAP advancement approach, NHTSA has developed a roadmap outlining the Agency’s phased NCAP upgrade plans over the next several years. The roadmap details near-term and long-term strategies for NCAP upgrades, adopting a gradual approach with phased proposed upgrades as technologies mature for NCAP inclusion. Each proposal will be followed by a final decision document responding to comments and outlining NHTSA’s decisions for that NCAP update phase, including implementation lead times. The roadmap presents an estimated timeframe for phased request for comment (RFC) notices.

Fifthly, this notice also considers expanding NCAP to provide consumer information on safety technologies that can help people drive safer by preventing or limiting risky driving behavior. The Agency is exploring expanding NCAP to include technologies that promote NHTSA’s ongoing efforts to combat unsafe driving behaviors like distracted and impaired driving, unrestrained driving, and speeding. While NHTSA currently employs various approaches to reduce dangerous driving behaviors, including high-visibility enforcement and advertising campaigns like “Click it or Ticket” and “Buzzed Driving is Drunk Driving,” these campaigns have achieved success but have not eliminated human-caused crashes. NHTSA is considering how NCAP can promote technologies that reduce unsafe driving or riding behaviors, targeting behaviors most likely to cause crashes. This information will be especially relevant for parents or caregivers shopping for vehicles for new or inexperienced drivers, or those seeking rear seat alerts for hot car/heatstroke prevention.

Sixthly and finally, this RFC discusses NHTSA’s ideas for updating several programmatic aspects of NCAP to enhance the program overall. NHTSA requests comments on revising the 5-star safety ratings program. This document also discusses NHTSA’s plans to update existing ADAS technology program components, outlines challenges related to manufacturer self-reported data, and proposes potential solutions. Lastly, this RFC addresses (1) NCAP website updates to improve consumer vehicle safety information dissemination and (2) developing an NCAP database to modernize program operations, including a new vehicle information submission process for manufacturers.

This RFC includes numbered questions throughout to highlight specific topics on which NHTSA seeks comments. Unnumbered questions within sections are reiterated at the end of each topic discussion and in Appendix B. To facilitate comment processing, NHTSA requests commenters to use corresponding numbering in their responses.

II. Background

NHTSA established NCAP in 1978 in response to Title II of the Motor Vehicle Information and Cost Savings Act of 1972. When NCAP first provided consumers with vehicle safety information from frontal crashworthiness testing, industry attention to vehicle safety was relatively nascent. Today, consumers are significantly more safety-conscious, making it a key vehicle purchasing factor[11]. Vehicle manufacturers have responded by offering safer vehicles with enhanced safety features, resulting in improved NCAP performance and higher star ratings.

Over time, NHTSA integrated ADAS technologies into NCAP’s crash avoidance program. In 2007, NHTSA issued an RFC exploring ADAS technology inclusion in NCAP[12]. Based on feedback, NHTSA published a final decision[13] expanding NCAP to include certain ADAS technologies and performance thresholds. Beginning with model year 2011, the Agency recommended forward collision warning (FCW), lane departure warning (LDW), and electronic stability control (ESC)[14] on its website, identifying vehicles with technologies meeting NCAP performance requirements. NCAP was further updated to include crash imminent braking (CIB) and dynamic braking support (DBS) technologies for model year 2018 vehicles onwards[14].

This RFC continues these efforts. Through notices and public meetings, NHTSA has engaged stakeholders on technologies for NCAP inclusion and their minimum performance thresholds. Appendix C details a history of RFCs, public meetings, and relevant events underpinning this notice.

The last NCAP change discussion RFC was published in 2015. It was broad, seeking comment on NCAP’s potential use of enhanced safety evaluation tools, star rating generation, and further vehicle safety development stimulation[15]. On crashworthiness, it sought comment on a new frontal oblique test and advanced crash test dummies across tests. It also sought comment on a new crash avoidance rating category with nine advanced crash avoidance technologies and a new pedestrian protection rating category involving adult and child head, upper leg, and lower leg impact tests and two new pedestrian crash avoidance technologies. The RFC explored combining crash avoidance, crashworthiness, and pedestrian protection into an overall 5-star rating. NHTSA held public hearings in Detroit, Michigan, on January 14, 2016, and in Washington, DC, on January 29, 2016, to gather comments, which are discussed later in this document.

In October 2018, NHTSA hosted a third public meeting to re-engage stakeholders and gather updated input for NCAP’s future[16]. The Agency has also worked to finalize research on pedestrian crash protection, advanced anthropomorphic test devices (crash test dummies) for frontal and side impacts, a new frontal oblique crash test, and an updated rollover risk curve. As detailed in the roadmap, NHTSA plans to phase in NCAP crashworthiness program upgrades over the next several years, leveraging acquired research knowledge.

III. ADAS Performance Testing Program

ADAS technologies offer significant safety potential by preventing crashes or mitigating the severity of crashes, reducing injuries and fatalities. NCAP currently conducts performance verification tests for four ADAS technologies: forward collision warning (FCW), lane departure warning (LDW), crash imminent braking (CIB), and dynamic brake support (DBS). CIB and DBS are collectively known as automatic emergency braking (AEB). Vehicles equipped with one or more of these systems and passing NCAP’s performance test requirements are listed as “Recommended” on NHTSA’s website. When FCW and LDW systems were first recommended for model year 2011 vehicles, their fitment rate was below 0.2 percent (fitment rate being the percentage of vehicles with a particular ADAS system). For model year 2018 vehicles, 38.3 percent were equipped with FCW and 30.1 percent with LDW[17]. Providing vehicle safety information through NCAP can effectively advance safer vehicle designs and technology deployment in the U.S. market, inform consumer choices, and encourage adoption of life-saving technologies.

With this notice, NHTSA proposes incorporating four additional ADAS technologies into NCAP’s crash avoidance program: lane keeping support (LKS), pedestrian automatic emergency braking (PAEB), blind spot warning (BSW), and blind spot intervention (BSI). Each technology meets the Agency’s established NCAP inclusion criteria: (1) addressing a safety need; (2) system designs to mitigate the problem; (3) safety benefit potential; and (4) objective performance test procedures[18]. Details on how each proposed ADAS technology addresses a safety need (criterion 1) are discussed below, while the remaining criteria are addressed in relevant sections for each technology.

To understand the safety need addressed by current ADAS technologies, NHTSA analyzed crash data for 84 mutually exclusive pre-crash scenarios[19]. These scenarios were based on a typology[20] concept[21] published by the Volpe National Transportation Systems Center (Volpe), categorizing crashes into dynamically distinct scenarios based on pre-crash vehicle movements and critical events. As detailed in a March 2019 report, NHTSA mapped pre-crash scenario typologies to twelve available ADAS technologies[22] believed to potentially mitigate certain pre-crash scenarios by assisting drivers in crash avoidance or mitigation. These mappings defined corresponding crash populations (target crash populations).

Since several ADAS technologies in passenger vehicles[23] mitigate the same crash scenarios, NHTSA grouped technologies with similar design intent into categories. The five technology categories resulting from this grouping are: (1) forward collision prevention, (2) lane keeping, (3) blind spot detection, (4) forward pedestrian impact, and (5) backing collision avoidance. As shown in Table A-6, these categories address high-level crash types: (1) rear-end; (2) rollover, lane departure, and road departure; (3) lane change/merge; (4) pedestrian; and (5) backing, respectively. Of the original 84 pre-crash scenarios, 34 relevant typologies were mapped to these five technology categories representing these crash types.

The forward collision prevention category included forward collision warning, crash imminent braking, and dynamic brake support (FCW, CIB, and DBS). The lane keeping category included lane departure warning (LDW), lane keeping support (LKS)[24], and lane centering assist (LCA). The blind spot detection category included blind spot warning (BSW)[25], blind spot intervention (BSI), and lane change/merge warning. The forward pedestrian impact avoidance category included pedestrian automatic emergency braking (PAEB). Lastly, the backing collision avoidance category included rear automatic braking (RAB) and rear cross-traffic alert (RCTA). These ADAS technologies are categorized as SAE International (SAE) Level 0-1 driving automation systems[26].

NHTSA derived target crash populations for each of the five technology categories using 2011-2015 Fatality Analysis Reporting System (FARS) and National Automotive Sampling System General Estimates System (NASS GES) data sets, records of police-reported fatal and non-fatal crashes, respectively, on U.S. roads. For each technology category, data for corresponding pre-crash scenarios was compiled to generate target crash populations encompassing crash numbers, fatalities, non-fatal injuries, and property-damage-only vehicles (PDOVs)[27]. Table 1 shows a breakdown of target crash populations per technology category.

Table 1—Summary of Target Crashes by Technology Group
| Safety systems | Crashes | Fatalities | MAIS 1-5 injuries | PDOVs |
|—|—|—|—|—|
| 1. FCW/DBS/CIB | 1,703,541 (29.4%) | 1,275 (3.8%) | 883,386 (31.5%) | 2,641,884 (36.3%) |
| 2. LDW/LKA/LCA | 1,126,397 (19.4%) | 14,844 (44.3%) | 479,939 (17.1%) | 863,213 (11.9%) |
| 3. BSW/BSI/LCM | 503,070 (8.7%) | 542 (1.6%) | 188,304 (6.7%) | 860,726 (11.8%) |
| 4. PAEB | 111,641 (1.9%) | 4,106 (12.3%) | 104,066 (3.7%) | 6,985 (0.1%) |
| 5. RAB/RvAB²⁸ RCTA | 148,533 (2.6%) | 74 (0.2%) | 35,268 (1.3%) | 231,317 (3.2%) |
| Combined | 3,593,18 (62%) | 20,841 (62.2%) | 1,690,963 (60.3%) | 4,604,125 (63.3%) |

It’s important to note that target crash populations for these five technology categories covered 62 percent of all crashes. Crossing path crashes, representing a large crash population and significant fatalities, were excluded because NHTSA is unaware of currently available ADAS technology effectively mitigating this crash type[29]. However, emerging safety countermeasures, including intersection safety assist (ISA) systems using onboard sensors (cameras, lidar, radar) and vehicle communications systems[30] [31], hold future potential and will be considered for NCAP as they mature. Loss-of-control in single-vehicle crashes[32] also had a relatively high target population and fatality rate[33], but were not included as, aside from mandated electronic stability control (ESC) systems[34], NHTSA is unaware of ADAS technology effectively preventing this crash type meeting NCAP inclusion criteria at this time[35].

Of pre-crash typologies in NHTSA’s March 2019 study, rear-end collisions were the most frequent crash type, averaging 1,703,541 annually, representing 29.4 percent of all annual crashes (5,799,883). Lane keeping typologies followed (1,126,397 crashes or 19.4 percent), and then blind spot detection-related crashes (503,070 crashes or 8.7 percent). Backing crashes (148,533) represented 2.6 percent, followed by forward pedestrian crashes (111,641) at 1.9 percent.

Rear-end collisions also had the highest number of Maximum Abbreviated Injury Scale (MAIS)[36] 1-5 injuries at 883,386, 31.5 percent of all non-fatal injuries (2,806,260). Lane keeping crashes had the second-highest injuries at 479,939 (17.1 percent), and blind spot crashes were third at 188,304 (6.7 percent). These were followed by forward pedestrian crashes at 3.7 percent and backing crashes at 1.3 percent[37] [38].

NHTSA found lane keeping technology categories, represented by rollover, lane departure, and road departure crashes, included the highest fatalities: 14,844, or 44.3 percent of all fatalities (33,477). Forward pedestrian impact category followed, with 4,106 pedestrian fatalities (12.3 percent). Forward collision prevention category, comprising rear-end crashes, included 1,275 fatalities (3.8 percent)[39]. Blind spot detection technology category, represented by lane change/merge crashes, accounted for 1.6 percent of all fatalities. Backing crashes followed at 0.2 percent, defining the backing collision avoidance category. Forward pedestrian crashes, comprising the forward pedestrian impact category, ranked second-highest in fatalities and were the deadliest based on fatalities per crash frequency.

In selecting ADAS technologies for this proposal, NHTSA aimed to target not only the most frequent crash types but also prioritize the most fatal and high-risk crashes. Based on studied target crash populations, NHTSA believes forward collision prevention, lane keeping, blind spot detection, and forward pedestrian impact technology categories address the most significant safety needs.

The Agency notes that ADAS technologies representing the backing collision avoidance category (RAB, RvAB, and RCTA) are not proposed for this program update. Backing collision avoidance category did not rank in the top third for crash number, fatalities, or MAIS 1-5 injuries, possibly due to FMVSS No. 111, “Rear visibility”[40]. Additional time is needed to assess real-world data and the effects of FMVSS No. 111 full implementation before considering backing crash prevention ADAS technologies in NCAP. While rear automatic braking (RAB) addition to NCAP was previously proposed in the December 2015 notice, ongoing test procedure changes and public comments necessitate further refinement, hence its exclusion from this proposal. ADAS technologies addressing backing pre-crash typologies may be proposed for NCAP as real-world data analysis and test procedure revisions continue.

Units of measure in this notice include meters (m), kilometers (km), millimeters per second (mm/s), meters per second (m/s), kilometers per hour (kph), feet (ft.), inches per second (in./s), feet per second (ft./s), miles per hour (mph), seconds (s), and kilograms (kg).

A. Lane Keeping Technologies

A 2005-2007 fatal crash study[41] from the National Motor Vehicle Crash Causation Study (NMVCCS)[42] identified that 42 percent of lane departure crashes (driver leaving lane before crash) resulted in rollovers and 37 percent in opposite direction crashes.

Analyzing NHTSA’s 2019 target population study, NHTSA believes lane keeping technologies like lane departure warning (LDW), lane keeping support (LKS), and lane centering assist (LCA) can address ten pre-crash scenarios, preventing or mitigating roadway departures and crossing centerlines or medians (opposite direction crashes). These pre-crash scenarios averaged 1.13 million annual crashes (19.4 percent of all U.S. crashes), resulting in 14,844 fatalities and 479,939 MAIS 1-5 injuries, as shown in Table A-2. This represents 44.3 percent of all fatalities and 17.1 percent of all injuries[43] [44].

NCAP currently provides performance information for LDW, a lane keeping ADAS technology introduced in the program in 2010 for model year 2011 vehicles[45]. At the time, LDW fitment rate was below 0.2 percent, rising to 30.1 percent in model year 2018[46]. While LDW adoption increased, it wasn’t as significant as forward collision warning (FCW), which saw a ~40 percent increase over the same period. A possible explanation for LDW’s lower fitment rate is discussed in the next section. Lane keeping support (LKS) is another lane keeping ADAS technology deemed appropriate for NCAP inclusion. NHTSA believes LKS may offer additional safety benefits beyond LDW and more effectively address fatalities and injuries from lane departure crashes.

1. Updating Lane Departure Warning (LDW)

Lane departure warning is a NHTSA-recommended technology in NCAP to mitigate lane departure crashes. LDW systems help prevent crashes when drivers unintentionally drift out of their lane. These systems often use camera-based sensors to detect lane markers (solid lines, dashed lines, raised reflective indicators like Botts’ Dots) ahead of the vehicle[47]. Lane departure alerts are given when the vehicle laterally approaches or crosses lane markings. Alerts may be visual, audible, and/or haptic[48]. Visual alerts may indicate the lane departure side, and haptic alerts may be steering wheel or seat vibrations. LDW alerts warn drivers of unintentional lane shifts, allowing them to steer back into lane. When turn signals are activated, LDW systems recognize intentional lane changes and do not alert drivers.

NHTSA plans to use the current NCAP test procedure, “Lane Departure Warning System Confirmation Test and Lane Keeping Support Performance Documentation,” dated February 2013[48], to assess LDW systems under NCAP. This protocol assesses a system’s alert issuance in response to unintended lane departures and quantifies vehicle position relative to lane lines upon LDW alert. NCAP’s LDW tests accelerate a test vehicle from rest to 72.4 kph (45 mph) in a straight line parallel to a single lane line of three types: continuous white lines, discontinuous (dashed) yellow lines, or discontinuous raised pavement markers (Botts’ Dots). The vehicle is driven with its centerline ~1.8 m (6 ft.) from the lane edge, maintaining this path and speed at least 61.0 m (200 ft.) before the start gate. At the start gate, the driver manually steers to achieve a lane departure with a target lateral velocity of 0.5 m/s (1.6 ft./s) relative to the lane line. The driver does not use turn signals or apply sudden inputs to accelerator, steering wheel, or brake pedals, maintaining constant speed throughout. The test ends when the vehicle crosses at least 0.5 m (1.7 ft.) over the lane line edge. The scenario is tested for left and right departures, and all three lane marking types, totaling six test conditions. Five repeated trials are performed per test condition.

LDW performance is assessed by examining vehicle proximity to the lane line edge upon LDW alert. LDW alerts must not occur when the vehicle’s lateral position, represented by a 2D polygon[49], is greater than 0.8 m (2.5 ft.) from the lane line inboard edge (the edge closest to the vehicle upon lane departure initiation) and must occur before lane departure exceeds 0.3 m (1 ft.). To pass, LDW systems must meet pass criteria for three of the first five valid individual trials[50] per departure direction and lane line type (60 percent) and for 20 of 30 trials overall (66 percent).

NCAP’s LDW test conditions represent pre-crash scenarios corresponding to a substantial portion of fatalities and injuries in real-world lane departure crashes. Volpe’s independent review of 2011-2015 FARS and GES data showed ~40 and 30 percent of fatalities in fatal road departure and opposite direction crashes, respectively, occurred when posted speed was 72.4 kph (45 mph) or less[51]. Similarly, data indicated 64 and 63 percent of injuries from road departure and opposite direction crashes, respectively, occurred when posted speed was 72.4 kph (45 mph) or less[51].

While travel speed was often unknown in FARS and GES crashes[52], when reported, ~6 and 9 percent of fatal road departure and opposite direction crashes, respectively, occurred at travel speeds of 72.4 kph (45 mph) or less[52]. Likewise, data showed 22 and 25 percent of police-reported non-fatal road departure and opposite direction crashes, respectively, occurred at 72.4 kph (45 mph) or less[52]. Volpe’s review suggests speeding is common in lane departure pre-crash scenarios, but most road departure and opposite direction-related fatalities and injuries did not occur on highways. 79 percent of road departure-related fatal crashes and 89 percent of road departure-related police-reported injuries occurred on non-highways. Similarly, for opposite direction crashes, 87 percent of fatalities and 98 percent of injuries occurred on non-highways. Given highway driving speeds are generally higher than non-highway speeds, Volpe’s data on crashes under 72.4 kph (45 mph) appears accurate. The 72.4 kph (45 mph) test speed addresses a large portion of crash travel speeds.

Furthermore, 62 percent of road departure-related fatalities and 76 percent of injuries occurred on straight roads, aligning with NCAP’s test procedure. For opposite direction crashes, 69 percent of fatalities and 67 percent of police-reported injuries occurred on straight roads.

In its December 2015 notice[53], NHTSA expressed concern that LDW technology safety benefits were diminished by false activations. Studies referenced in that notice found drivers disabling LDW systems due to frequent nuisance alerts. The Agency also worried about missed detections from sunlit or water-covered tar lines and other anomalies causing unreliable warnings. To address these issues and improve consumer acceptance, NHTSA requested comment in 2015 on revising certain aspects of NCAP’s LDW test procedure. Specifically, the Agency sought comment on feasibility of (1) awarding NCAP credit to LDW systems providing only haptic alerts, and (2) developing additional test scenarios for false activations and missed detections. The Agency also proposed tightening the inboard lane tolerance for LDW tests from 0.8 to 0.3 m (2.5 to 1.0 ft.). This proposal effectively increased the space within a lane before LDW alert triggering was permitted, requiring alerts to occur within a window of +0.3 to −0.3 m (+1.0 to −1.0 ft.) of the lane line’s inside edge to pass NCAP’s LDW procedure. Each topic is discussed below.

a. Haptic Alerts

Regarding haptic warnings, NHTSA noted in its December 2015 notice that these alerts may have greater consumer acceptance than audible alerts, improving LDW alert effectiveness if drivers don’t see alerts as nuisances and disable the system. In response to the notice, commenters generally did not support a haptic alert requirement. Some suggested requiring specific feedback types would limit manufacturer flexibility in issuing warnings, especially considering potential feedback type effectiveness and the need to optimize human-machine interface (HMI) designs for ADAS suites. Bosch suggested allowing all warning options to promote system availability in more vehicles, increasing consumer awareness and encouraging vehicle safety improvements. Advocates called for details on different sensory feedback effectiveness (visual, auditory, haptic) to justify encouraging one type over another. Consumers Union (CU) suggested crediting all LDW feedback types and awarding extra points/credit for haptic alerts to encourage this feedback type in the future. The Automotive Safety Council (ASC) acknowledged haptic warnings may improve driver acceptance of LDW systems but suggested false activations must also be reduced for improved consumer acceptance and safety benefits.

In a large-scale telematics-based UMTRI study[54] for NHTSA on LDW usage, researchers studied driver behavior in reaction to alerts. Two vehicle types were included: vehicles with audible-only alerts and vehicles where drivers could select audible or haptic alerts. When haptic alerts were available, drivers selected them 90 percent of the time. Otherwise, LDW systems were turned “off” 38 percent of the time. For systems with only audible warnings, LDW was turned “off” 71 percent of the time.

Based on UMTRI’s research, NHTSA concludes haptic alerts improve driver acceptance of LDW systems. However, the Agency is uncertain if increased acceptance will translate to improved LDW system efficacy in crash reduction. Furthermore, NHTSA does not want to hinder HMI design optimization given the increasing ADAS technologies in vehicles. Therefore, the Agency has decided not to require a specific alert modality for LDW warnings in its NCAP test procedure at this time, but requests comment on this decision’s appropriateness. While NHTSA has limited data on different alert type effectiveness, it shares concerns (similar to FCW) that certain LDW systems, like visual-only alerts, may be less effective than other options in medium or high urgency situations[55].

b. False Positive Tests

In response to the 2015 RFC, vehicle manufacturers and suppliers asserted that additional false positive test requirements were unnecessary, even acknowledging NHTSA’s concern about nuisance alert effects on consumer acceptance. The Alliance[56] stated manufacturers optimize systems to minimize false positive activations for consumer acceptance, making such tests unnecessary. Honda similarly stated manufacturers already account for false positives when considering marketability and HMI, finding it difficult for the Agency to create a valid, robust, and repeatable false positive test procedure. Mobileye, Bosch, and MTS Systems Corporation (MTS) concurred. Mobileye explained difficulty reproducing exact test conditions, especially weather, across test locations. Bosch stated specialized tests may not represent all real-world driving situations. MTS alternatively suggested adding a new test to NCAP’s LDW procedure to assess whether LDW systems can inform drivers of warning unavailability due to poor environmental conditions.

Given concerns about repeatability and reproducibility of test conditions, and the Agency’s current data not supporting false positive assessment for lane keeping technologies, NHTSA continues monitoring consumer complaint data on false positives to inform next steps.

Regarding MTS’s recommendation, the Agency acknowledges vehicle manufacturers install LDW telltales on instrument panels to inform drivers when systems are operational. Systems are typically operational when vehicle speed reaches a preset threshold and lane markings and environmental conditions are suitable. The telltale disappears if conditions are unmet, informing drivers the system is no longer operational and will not alert for lane departures. Given this feature, NHTSA has decided a test to inform drivers of warning unavailability is currently unnecessary.

c. LDW Test Procedure Modifications

Support varied regarding NHTSA’s 2015 notice proposal to reduce lane line tolerance for system activation from 0.8 to 0.3 m (2.5 to 1.0 ft.). Global Automakers stated the proposed change was “unduly prescriptive” and recommended retaining existing lane line tolerance. They explained research showed 90 percent of drivers need 1.2 s to react to warnings[57]. Citing NCAP’s LDW test procedure requiring steering input with a target lateral velocity of 0.5 to 0.6 m/s (1.6 to 2 ft./s), the trade association noted this equated to a necessary warning distance of 0.6 to 0.72 m (1.9 to 2.4 ft.) for 90 percent of drivers to react in time to prevent lane departure. Advocates agreed nuisance notifications are a concern for driver acceptance, but noted the Agency provided limited information on LDW system effectiveness meeting proposed criteria. Conversely, Delphi, ASC, and MTS commented that more robust systems could comply with the narrower specification. However, ASC suggested evaluating the proposed changes’ impact before finalizing requirements to ensure narrower tolerances reduce false positive alerts and improve consumer acceptance of LDW systems. Mobileye stated tolerance reduction should increase required accuracy and quality of lane keeping systems. MTS remarked tighter specification systems would yield higher driver satisfaction and system use compared to current requirements. Hyundai Motor Company (Hyundai) also supported the tolerance revision. Consumers Union (CU) agreed narrowed lateral tolerance should reduce false alerts on main roadways but cautioned it may not effectively address false alerts on secondary or curved roads, where vehicles may approach or cross lane lines within one foot. They suggested false alert conditions be subject to speed limitations or GPS-based position sensors to avoid “over activation” on secondary or curved roads.

Given NHTSA’s goal of reducing nuisance notifications to increase consumer acceptance of LDW systems and commenter statements that current LDW systems can meet the proposed reduced test specification, the Agency believes proposing the reduced inboard lane tolerance of 0.3 m (1.0 ft.) is reasonable.

Besides comments on lane line tolerance, the Agency received suggestions to adopt additional test scenarios or procedural modifications for NCAP’s LDW test procedure. Similar to CU’s curved road suggestion, Mobileye suggested adding inner and outer curve scenarios allowing larger tolerance for inner lane boundaries than straight roads. They further recommended adding road edge detection scenarios, including curbs and non-structural delimiters like gravel or dirt, to better reflect real-world conditions and crash scenarios. Bosch also suggested considering road edge detection requirements beyond lane markings as not all roads have markings. Additionally, Mobileye suggested altering Botts’ Dots detail #4 (round, raised lane markers) to align with more common California detail #13, and modifying the test procedure to include Botts’ Dots on both lane sides or Botts’ Dots and solid lines, as these are the most frequent pairings.

The Agency appreciates commenter suggestions and agrees on the merit of considering other procedural modifications for NCAP’s lane departure test procedure(s). As discussed next, the Agency plans a feasibility study to determine if curved roads can be objectively included in NCAP test procedures for LKS systems. NHTSA also plans research to assess how lane keeping system performance on test tracks compares to real-world data for different combinations of curve radius, vehicle speed, and departure timing. The Agency recognizes the European NCAP program (Euro NCAP) has adopted a road edge detection test similar to their “lane keep assist” tests (described next), but without lane markings. While NHTSA believes vehicles recognizing and responding to road edges without lane lines are currently few, it recognizes roadways where this capability could prevent crashes. Therefore, the Agency requests comment on whether a road edge detection test for LDW and/or LKS is appropriate for NCAP inclusion. Regarding current lane markings, the Agency proposes removing the Botts’ Dots test scenario from the current LDW test, as this lane marking type is being phased out in California[58]. At this time, the Agency believes traditional dashed and solid lane marking tests suffice.

Although NHTSA tentatively decided against additional false activation requirements for this NCAP upgrade, the Agency remains concerned about LDW’s low effectiveness and consumer acceptance stemming from nuisance alerts and missed detections.

When NHTSA decided to include ADAS in NCAP in 2008[59], LDW was selected because it met NCAP’s four criteria: (1) addressing a major crash problem; (2) LDW system design mitigating the crash problem; (3) projected safety benefits; and (4) test procedures and evaluation criteria ensuring acceptable performance. At the time, the Agency estimated LDW systems were 6-11 percent effective in preventing lane departure crashes. While system effectiveness was relatively low, NHTSA cited the large number of road departure and opposite direction crashes and resulting AIS 3+ injuries as reasons to include LDW in NCAP. Recent studies have shown varying LDW effectiveness results.

A 2017 IIHS study[60] concluded LDW systems reduced passenger car crashes (single-vehicle, side-swipes, and head-on) by 11 percent, consistent with NHTSA’s initial estimate. Importantly, IIHS also concluded LDW systems reduced injuries in these crash types by 21 percent. In its recent study on real-world effectiveness of crash avoidance technologies in GM vehicles[61], UMTRI found LDW systems showed a non-statistically significant 3 percent reduction in applicable crashes. Conversely, active safety technology, LKS (including lane departure warning), showed an estimated 30 percent reduction in applicable crashes.

Other studies examining driver deactivation rates also suggest LDW effectiveness may be lower than initially estimated. In a survey of Honda vehicles at dealerships for service[62], IIHS researchers found only a third of 184 LDW-equipped models had the system activated. Furthermore, UMTRI’s telematics-based LDW usage study[63] found drivers turned off LDW systems 50 percent of the time overall. However, in Consumer Reports’ August 2019 survey of over 57,000 CR subscribers, 73 percent of vehicle owners reported LDW technology satisfaction. 33 percent said the system helped avoid a crash, and 65 percent trusted it to work every time[64].

Given these findings, the Agency believes, alongside LDW, adopting an active lane keeping system like lane keeping support (LKS) in NCAP is merited. As an enhanced active system, LKS offers steering and/or braking capabilities to guide vehicles back into lanes without consumer action, potentially enhancing safety benefits beyond LDW. A detailed LKS technology discussion follows.

2. Adding Lane Keeping Support (LKS)

LDW systems warn drivers of unintentional lane drifts, while lane keeping support (LKS) systems actively guide drifting vehicles back into lanes by gently counter-steering or applying differential braking. During unintentional lane departures without turn signals, LKS systems help prevent: “Sideswiping” (striking adjacent vehicles in same direction lanes); opposite direction crashes (crossing centerlines and striking oncoming vehicles); and road departure crashes (running off-road, resulting in rollovers or impacts with trees/objects). LKS systems may also prevent unintended lane departures into designated bicycle lanes if speed thresholds are met.

LKS systems typically use the same camera(s) as LDW systems to monitor vehicle lane position and determine unintentional lane drift. LKS automatically intervenes by: braking vehicle wheels; steering; or using braking and steering combinations to return vehicles to intended lanes. LKS is one of two active lane keeping technologies in the Agency’s March 2019 report[65], the other being lane centering assist (LCA). LKS assists drivers with short-duration steering and/or braking inputs when lane departures are imminent or underway, while LCA provides continuous driver assistance to keep vehicles centered in lanes.

As discussed, UMTRI evaluated ADAS technology real-world effectiveness, including LDW and LKS[66]. LKS study results (including LDW) showed an estimated 30 percent reduction in applicable crashes. Additionally, in its August 2019 survey, 74 percent of vehicle owners reported LKS technology satisfaction, with 35 percent reporting it helped avoid crashes. Sixty-five percent of owners trusted the system to work every time[67].

In its December 2015 notice, NHTSA did not propose including LKS technology in NCAP updates. However, many commenters recommended Agency consideration. Bosch and Mobileye stated LKS systems could prevent or mitigate more injury and fatality collisions than LDW systems. ASC and Delphi recommended adopting LKS instead of LDW, with ASC noting Euro NCAP included LKS in its Lane Support Systems test protocol since 2016[68] [69]. ASC, Bosch, and Continental noted LKS technology maturity and wide availability in vehicles at the time. Other LKS technology adoption proponents include the National Safety Council (NSC), ZF TRW, and Honda. ZF TRW recommended adopting both active lane keeping (LKS) and lane centering systems (LCA) due to high fatal road departure crash frequency. Honda also supports LKS active safety benefits and crash prevention potential. NSC suggested including LKS to complement LDW, similar to FCW’s warning component complementing AEB’s active safety functionality.

As previously mentioned, the Agency agrees with commenters on LKS technology adoption merit in NCAP. However, NHTSA believes an LDW system integrated with LKS may be a better approach than replacing LDW with LKS. NHTSA believes, as NSC commented, an integrated approach (passive and active lane support systems) would be similar to frontal collision avoidance systems, FCW and AEB, proposed later in this notice.

NHTSA is considering adopting test methods (e.g., “lane keep assist”) from the Euro NCAP Test Protocol—Lane Support Systems (LSS)[70] to assess LKS technology design differences. Since test speeds and road configurations in this protocol are similar to the Agency’s LDW test procedure, the Agency believes Euro NCAP’s test protocol will sufficiently address the lane keeping crash typology previously detailed for LDW.

Euro NCAP’s LSS test procedure includes “lane keep assist” trials with iteratively increasing lateral velocities toward the desired lane line. Each “lane keep assist” trial begins with the subject vehicle (SV) being driven at 72 kph (44.7 mph) down a straight lane marked by a single solid white or dashed white line. Initially, the SV path is parallel to the lane line, with an offset depending on the lateral velocity used later. After steady-state driving, SV direction heads towards the lane line using a 1,200 m (3,937.0 ft.) radius curve. SV lateral velocity towards the lane line (left and right directions) increases from 0.2 to 0.5 m/s (0.7 to 1.6 ft./s) in 0.1 m/s (0.3 ft./s) increments until acceptable LKS performance is no longer achieved. Acceptable LKS performance occurs when the SV does not cross the lane line inboard leading edge by more than 0.3 m (1.0 ft.).

NHTSA conducted a limited assessment of five model year 2017 vehicles with LKS systems, using a robotic steering controller for repeatability and variability minimization from manual steering inputs. This study used a slightly modified, older version of Euro NCAP’s LSS test procedure. Specifically, SV lateral velocity towards the lane line increased from 0.1 m/s to 1.0 m/s in 0.1 m/s increments (0.3 ft./s to 3.3 ft./s in 0.3 ft./s increments) to assess LKS system performance at higher velocities. LKS performance was deemed acceptable (compared to Euro NCAP’s assessment criteria at the time of NHTSA testing) when the SV did not cross the lane line inboard leading edge by more than 0.4 m (1.3 ft.)[71].

Preliminary analysis of the five tested vehicles identified performance differences based on lateral velocity during testing. Some vehicles only engaged steering response at lower velocities, others continued steering input as lateral velocity increased[72]. Maximum lane marking excursion after LKS activation was also inconsistent, especially with increased lateral velocity. These preliminary findings indicated performance differences in how manufacturers design systems for given operating conditions.

Results from these tests, measured by maximum lane marking excursions, were compared to road shoulder widths where fatal road departure crashes occurred. The analysis identified roadways with shoulder widths less than the 0.4 m (1.3 ft.) maximum excursion limit (e.g., certain rural roadways) used in Agency testing. It was observed that only vehicles with robust LKS performance, including at higher lateral velocities, would likely prevent lane departures on these roadways. However, most roadway departure crashes occurred on roads with shoulder widths exceeding 0.4 m (1.3 ft.). On these roadways, assuming LKS engagement, lane departures could have been avoided. However, some vehicles performed poorly, with no system intervention and others exceeding maximum excursion limits with increasing lateral velocity. Additional LKS testing has since been conducted to supplement these initial findings and is currently undergoing analysis.

Since the analysis showed most fatal crashes studied were on roadways with shoulder widths exceeding the current Euro NCAP test excursion limit of 0.3 m (1.0 ft.), NHTSA believes adopting the Euro NCAP criterion may provide significant safety benefits but requests comment on whether an even smaller excursion limit might be more appropriate. Furthermore, as the study identified fatal crashes where lane markers were absent on the departure side (meaning LKS would not benefit unless it could identify road edges), the Agency requests comment (as previously mentioned) on adding Euro NCAP’s road edge detection test to NCAP to address crashes in areas lacking lane markings.

Based on NHTSA’s LKS testing findings, showing LKS performance differences at higher lateral velocities, the Agency is concerned about LKS performance at higher speeds when vehicles transition from straight to curved roads with inherently high lateral velocity. Volpe’s 2011-2015 FARS data analysis found 29 percent of fatal road departure crashes and 26 percent of fatal opposite direction crashes occurred at known speeds exceeding 72.4 kph (45 mph). Analysis also showed 55 percent of fatal road departure crashes and 67 percent of opposite direction crashes occurred on roads with posted speeds over 72.4 kph (45 mph)[73] [74]. Speeding was a factor in 31 percent and 13 percent of fatal road departure and opposite direction crashes, respectively[75]. As NHTSA lacks data showing LKS system performance at Euro NCAP’s 72 kph (44.7 mph) test speed is indicative of higher speed performance, NHTSA requests comment on whether incorporating additional, higher test speeds to assess lane keeping system performance in NCAP would be beneficial.

To date, NHTSA has only performed test track LKS evaluations using the straight road test configuration from Euro NCAP’s test procedure. However, the Agency recognizes a significant portion of road departure and opposite direction crashes resulting in fatalities and injuries occur on curved roads. Volpe’s 2011-2015 data set review[76] showed that for road departure crashes, 37 percent of fatalities and 20 percent of injuries occurred on curved roads. For opposite direction crashes, 30 percent of fatalities and 31 percent of injuries occurred on curved roads. NHTSA is uncertain how LKS performance in straight road trials on test tracks correlates to real-world curved road system performance. However, NHTSA believes, based on on-road performance testing of newer models, some current system designs address lane departures on curved roads. The Agency observed some LKS systems engage with limited operation throughout curves, offering minimal safety benefits. More sophisticated LKS systems maintain engagement longer, offering more directional authority throughout curves, potentially providing additional safety gains by giving drivers more time to re-engage (restore effective manual vehicle control).

In NHTSA’s 2005-2007 fatal crash study[77] from NMVCCS, curved road crashes[78] with lane departure were analyzed. Unlike straight roads where LKS systems may provide smaller corrective steering inputs to prevent lane departure, LKS systems on curved roads would need sustained lateral correction (corrective steering) to prevent lane departure.

Furthermore, in fleet testing of select 2012-2018 model year vehicles with LDW and LKS (referred to as LKA in the report), Transport Canada[79] found test result variability and generally unpredictable system behavior on curved roads. Transport Canada concluded insufficient data could be gathered to assess potential technology safety benefits.

To address these unknowns and further understand LKS system effectiveness, the Agency is considering additional research to study curved road testing for objective LKS system evaluation, and to collect test track and real-world data to quantify LKS system operation under different combinations of curve radius, vehicle speed, and departure timing (e.g., at curve onset or midway through curve).

With respect to LDW and LKS, NHTSA seeks comment on the following:

(1) Should the Agency award credit to vehicles equipped with LDW systems that provide a passing alert, regardless of the alert type? Why or why not? Are there any LDW alert modalities, such as visual-only warnings, that the Agency should not consider acceptable when determining whether a vehicle meets NCAP’s performance test criteria? If so, why? Should the Agency consider only certain alert modalities (such as haptic warnings) because they are more effective at re-engaging the driver and/or have higher consumer acceptance? If so, which one(s) and why?

(2) If NHTSA were to adopt the lane keeping assist test methods from the Euro NCAP LSS protocol for the Agency’s LKS test procedure, should the LDW test procedure be removed from its NCAP program entirely and an LDW requirement be integrated into the LKS test procedure instead? Why or why not? For systems that have both LDW and LKS capabilities, the Agency would simply turn off LKS to conduct the LDW test if both systems are to be assessed separately. What tolerances would be appropriate for each test, and why?

(3) LKS system designs provide steering and/or braking to address lane departures (e.g., when a driver is distracted)[80]. To help re-engage a driver, should the Agency specify that an LDW alert must be provided when the LKS is activated? Why or why not?

(4) Do commenters agree that the Agency should remove the Botts’ Dots test scenario from the current LDW test procedure since this lane marking type is being removed from use in California[81]? If not, why?

(5) Is the Euro NCAP maximum excursion limit of 0.3 m (1.0 ft.) over the lane marking (as defined with respect to the inside edge of the lane line) for LKS technology acceptable, or should the limit be reduced to account for crashes occurring on roads with limited shoulder width? If the tolerance should be reduced, what tolerance would be appropriate and why? Should this tolerance be adopted for LDW in addition to LKS? Why or why not?

(6) In its LSS Protocol, Euro NCAP specifies use of a 1,200 m (3,937.0 ft.) curve and a series of increasing lateral offsets to establish the desired lateral velocity of the SV towards the lane line it must respond to. Preliminary NHTSA tests have indicated that use of a 200 m (656.2 ft.) curve radius provides a clearer indication of when an LKS intervention occurs when compared to the baseline tests performed without LKS, a process specified by the Euro NCAP LSS protocol. This is because the small curve radius allows the desired SV lateral velocity to be more quickly established; requires less initial lateral offset within the travel lane; and allows for a longer period of steady state lateral velocity to be realized before an LKS intervention occurs. Is use of a 200 m (656.2 ft.) curve radius, rather than 1,200 m (3,937.0 ft.), acceptable for inclusion in a NHTSA LKS test procedure? Why or why not?

(7) Euro NCAP’s LSS protocol specifies a single line lane to evaluate system performance. However, since certain LKS systems may require two lane lines before they can be enabled, should the Agency use a single line or two lines lane in its test procedure? Why?

(8) Should NHTSA consider adding Euro NCAP’s road edge detection test to its NCAP program to begin addressing crashes where lane markings may not be present? If not, why? If so, should the test be added for LDW, LKS, or both technologies?

(9) The LKS and “Road Edge” recovery tests defined in the Euro NCAP LSS protocol specify that a range of lateral velocities from 0.2 to 0.5 m/s (0.7 to 1.6 ft./s) be used to assess system performance, and that this range is representative of the lateral velocities associated with unintended lane departures (i.e., not an intended lane change). However, in the same protocol, Euro NCAP also specifies a range of lateral velocities from 0.3 to 0.6 m/s (1.0 to 2.0 ft./s) be used to represent unintended lane departures during “Emergency Lane Keeping—Oncoming vehicle” and “Emergency Lane Keeping—Overtaking vehicle” tests. To encourage the most robust LKS system performance, should NHTSA consider a combination of the two Euro NCAP unintended departure ranges, lateral velocities from 0.2 to 0.6 m/s (0.7 to 2.0 ft./s), for inclusion in the Agency’s LKS evaluation? Why or why not?

(10) As discussed above, the Agency is concerned about LKS performance on roads that are curved. As such, can the Agency correlate better LKS system performance at higher lateral velocities on straight roads with better curved road performance? Why or why not? Furthermore, can the Agency assume that a vehicle that does not exceed the maximum excursion limits at higher lateral velocities on straight roads will have superior curved road performance compared to a vehicle that only meets the excursion limits at lower lateral velocities on straight roads? Why or why not? And lastly, can the Agency assume the steering intervention while the vehicle is negotiating a curve is sustained long enough for a driver to re-engage? If not, why?

(11) The Agency would like to be assured that when a vehicle is redirected after an LKS system intervenes to prevent a lane departure when tested on one side, if it approaches the lane marker on the side not tested, the LKS will again engage to prevent a secondary lane departure by not exceeding the same maximum excursion limit established for the first side. To prevent potential secondary lane departures, should the Agency consider modifying the Euro NCAP “lane keep assist” evaluation criteria to be consistent with language developed for NHTSA’s BSI test procedure to prevent this issue? Why or why not? NHTSA’s test procedure states the SV BSI intervention shall not cause the SV to travel 0.3 m (1 ft.) or more beyond the inboard edge of the lane line separating the SV travel lane from the lane adjacent and to the right of it within the validity period. To assess whether this occurs, a second lane line is required (only one line is specified in the Euro NCAP LSS protocol for LKS testing). Does the introduction of a second lane line have the potential to confound LKS testing? Why or why not?

(12) Since most fatal road departure and opposite direction crashes occur at higher posted and known travel speeds, should the LKS test speed be increased, or does the current test speed adequately indicate performance at higher speeds, especially on straight roads? Why or why not?

(13) The Agency recognizes that the LKS test procedure currently contains many test conditions (i.e., line type and departure direction). Is it necessary for the Agency to perform all test conditions to address the safety problem adequately, or could NCAP test only certain conditions to minimize test burden? For instance, should the Agency consider incorporating the test conditions for only one departure direction if the vehicle manufacturer provides test data to assure comparable system performance for the other direction? Or, should the Agency consider adopting only the most challenging test conditions? If so, which conditions are most appropriate? For instance, do the dashed line test conditions provide a greater challenge to vehicles than the solid line test conditions?

(14) What is the appropriate number of test trials to adopt for each LKS test condition, and why? Also, what is an appropriate pass rate for the LKS tests, and why?

(15) Are there any aspects of NCAP’s current LDW or proposed LKS test procedure that need further refinement or clarification? Is so, what additional refinements or clarifications are necessary?

B. Blind Spot Detection Technologies

NHTSA’s 2019 target population study showed blind spot detection technologies like blind spot warning (BSW), blind spot intervention (BSI), and lane change/merge warning (LCM) (essentially a BSI warning system) can help prevent or mitigate five pre-crash lane change/merge scenarios. These pre-crash movements averaged 503,070 annual crashes, 8.7 percent of all U.S. crashes, resulting in 542 fatalities and 188,304 MAIS 1-5 injuries, as shown in Table A-3. This equates to 1.6 percent of fatalities and 6.7 percent of injuries recorded[82].

Currently, NCAP includes no ADAS technology designed to address blind spot pre-crash scenarios. NHTSA requested comment on BSW inclusion in its 2015 program update. While BSI wasn’t proposed for inclusion then, the Agency now proposes adopting both BSW and BSI technologies in this program update.

While the target population for blind spot detection technology may be smaller than AEB or lane keeping technologies, NHTSA believes blind spot technologies merit NCAP inclusion. Consumer Reports’ 2019 survey found 82 percent of vehicle owners satisfied with BSW technology, 60 percent said it helped avoid crashes, and 68 percent trusted the system to work every time[83]. The Agency believes the technology’s high consumer acceptance and potential safety benefits, discussed later, support its inclusion in NCAP.

1. Adding Blind Spot Warning (BSW)

A BSW system is a warning-based driver assistance system helping drivers recognize other vehicles approaching or operating within their blind spot in adjacent lanes. In these situations, and for all production BSW systems known to NHTSA, the BSW alert is automatically presented, most relevant to drivers contemplating or initiating lane changes. Depending on system design, additional BSW features may activate if the system is alerting and the driver operates their turn signal.

BSW systems use camera, radar, or ultrasonic-based sensors, or combinations thereof, typically located on vehicle sides and/or rear. BSW alerts may be auditory, visual (most common), or haptic. Visual alerts are often presented in side outboard mirror glass, inside mirror housing edges, or at front a-pillar bases inside the vehicle. When another vehicle enters or approaches the driver’s blind spot in an adjacent lane, the BSW visual alert is usually continuously illuminated. However, if drivers engage turn signals towards the adjacent vehicle while the visual alert is active, the alert may flash and/or be supplemented by auditory or haptic alerts (beeping or steering wheel/seat vibration).

NHTSA requested comment on a draft research blind spot detection (BSD) test procedure (herein BSW), published November 21, 2019[84], to assess system performance and capabilities in blind spot-related pre-crash scenarios. This procedure exercises BSW systems in two test track scenarios: Straight Lane Converge and Diverge Test, and Straight Lane Pass-by Test. These assess whether BSW systems warn when principal other vehicles (POVs) are in the driver’s blind spot, without tested vehicle (subject vehicle, SV) turn signal activation. Neither SV nor POV turn signals should be activated during any test trial. A brief description of each test scenario and passing result requirements follows:

Straight Lane Converge and Diverge Test—The SV and POV travel in adjacent lanes at 72.4 kph (45 mph). In the converge test, the POV initiates a lane change towards the SV from an adjacent lane. In the diverge test, the POV initiates a lane change away from the SV into an adjacent lane.
- To pass a test trial: during converge lane changes, BSW alerts must be presented no later than 300 ms after any POV part enters the SV blind zone and remain active while any POV part is within the SV blind zone; and during diverge lane changes, BSW alerts may remain active only when the lateral distance between SV and POV is >3 m (9.8 ft.) but ≤6 m (19.7 ft.). BSW alerts must deactivate once the lateral distance between SV and POV exceeds 6 m (19.7 ft.).
Straight Lane Pass-by Test—The POV approaches and passes the SV in an adjacent lane. For each trial, the SV travels at a constant 72.4 kph (45 mph), while the POV travels at one of four constant speeds: 80.5, 88.5, 96.6, or 104.6 kph (50, 55, 60, or 65 mph). Lateral distance between vehicles, defined as the closest lateral distance between adjacent sides of polygons representing each vehicle, should nominally be 1.5 m (4.9 ft.) for the trial duration. This test is repeated for POV approaches towards the SV from adjacent lanes left and right of the SV.
- To pass a trial, BSW alerts must be presented no later than 300 ms after the POV’s front-most part enters the SV blind zone and remain active while the POV’s front-most part remains behind the SV blind zone’s front-most part. BSW alerts must deactivate once the longitudinal distance between the SV’s front-most part and POV’s rear-most part exceeds the BSW termination distance specified for each POV speed.

For BSW tests, each scenario is tested using seven repeated trials for each combination of approach direction (SV left and right side) and test speed. This totals 14 tests overall for the Straight Lane Converge and Diverge Test and 56 for the Straight Lane Pass-by Test. NCAP proposes that to meet NCAP system performance requirements, SVs must pass at least five of seven trials for each approach direction and test speed combination.

Proposed BSW tests represent pre-crash scenarios corresponding to a substantial portion of fatalities and injuries in real-world lane change crashes. Volpe’s 2011-2015 data set review showed ~28 percent of fatalities and 57 percent of injuries in lane change crashes occurred on roads with posted speeds of 72.4 kph (45 mph) or lower[86]. For crashes with reported travel speeds in FARS and GES, ~14 percent of fatalities and 24 percent of injuries occurred at speeds of 72.4 kph (45 mph) or lower[87]. Furthermore, Volpe found speeding a factor in only 18 percent of fatal lane change crashes and 3 percent of injury-resulting lane change crashes[88 [89]. This suggests posted speed aligns well with travel speed in most lane change crashes.

Consumer Reports (CR) market research indicated BSW systems are desirable in consumer interest surveys of ADAS technologies. CR found most vehicle owners satisfied with BSW technology, and 60 percent believed BSW technology helped them avoid crashes. However, UMTRI’s study evaluating ADAS technology real-world effectiveness in 2013-2017 General Motors’ (GM) vehicles found GM’s Side Blind Zone Alert produced a non-significant 3 percent lane change crash reduction. When Side Blind Zone Alert technology combined with GM’s earlier generation Lane Change Alert, effectiveness increased to 26 percent[90]. UMTRI attributed this increase to substantially longer vehicle detection ranges for the Lane Change Alert with Side Blind Zone Alert system versus GM’s earlier Side Blind Zone Alert system[91]. An Agency study of three BSW-equipped vehicles also showed current BSW systems may exhibit detection capability and operating condition differences, leading to significant effectiveness estimate variations[92]. For instance, one vehicle’s system might augment driver visual awareness, while another could effectively prevent crashes by warning of higher-speed lane change events. Bosch provided similar insight in its response to NCAP’s December 2015 notice, stating some BSW systems may only benefit for shorter detection distances, like 7 m (23.0 ft.) rearward, while others may detect up to 70 m (229.7 ft.) rearward, helping drivers avoid collisions with rear-approaching vehicles in adjacent lanes at high speeds. The Agency plans to study these performance differences in testing.

NHTSA proposes conducting BSW tests in NCAP per the Agency’s BSW test procedure. The Agency believes the Straight Lane Pass-by Test scenario, stipulating incrementally higher POV test speeds, could differentiate between basic and advanced BSW capabilities. For example, SVs satisfying BSW activation criteria only when POVs approach with low relative velocity might be considered basic BSW capability, while vehicles sensing further rearward to detect faster-passing vehicles may be considered superior BSW capability. NHTSA believes such assessment is important because higher speed differential crashes are expected to be more severe than those with similar vehicle speeds. Furthermore, extended rear zone vehicle detection capability could be important for other ADAS technologies like blind spot intervention (BSI) or SAE[93] Level 2 partial driving automation[94] systems incorporating automatic lane change features. Therefore, long-range vehicle detection may not only increase blind spot technology effectiveness, such as BSI, but also enhance capabilities and robustness of other ADAS applications. For these reasons, NHTSA proposes (later in this notice) BSI technology incorporation in NCAP to encourage proliferation and sensing strategies offering greater fields of view.

Commenters on NHTSA’s December 2015 notice overwhelmingly supported BSW addition to NCAP, with many suggesting expanding testing to include motorcycle detection and more test conditions. Several commenters also recommended NHTSA harmonize BSW test procedures with International Organization for Standardization (ISO) standards. Each topic is discussed below.

a. Additional Test Targets and/or Test Conditions

Commenters, including ASC, Continental, Bosch, NSC, and others, recommended expanding BSW testing requirements to include motorcycle detection. Delphi, MTS, Medical College of Wisconsin (MCW), and CU suggested evaluating vehicle ability to detect bicycles in addition to motorcycles. Subaru suggested Straight Lane Pass-by Test changes to address motorcycle detection. MTS and MCW added motorcycle riders and bicyclists are more vulnerable to serious and fatal injuries than motor vehicle occupants. A few commenters opposed motorcycle detection tests in NCAP. Global Automakers and Hyundai stated, while a reasonable future goal, no standardized test devices existed at the time. Honda and the Alliance recommended focusing on vehicle detection first as no standard motorcycle detection test procedure existed. The Alliance added motorcycle lane position varies greatly, requiring test procedures to specify motorcycle behavior and reasonable detection distances. MTS stated motorcycle POV lane position (near, center, far) should be specified, and motorcycle radar cross section and projected area considered.

NHTSA agrees BSW systems detecting motorcycles would improve safety. 2011-2015 FARS and GES data review[95] showed ~106 fatal and ~5,100 police-reported annual crashes, on average, for same direction lane change crashes involving vehicles and motorcycles. Comparatively, as mentioned, there were ~542 fatalities and ~503,070 police-reported annual crashes, on average, for lane change crashes involving motor vehicles. Data shows more motor vehicle occupants die in lane changing crashes than motorcyclists. However, motorcyclist fatality rates are greater than vehicle occupants.

At this time, the Agency prioritizes BSW system testing on motor vehicles for NCAP. NHTSA believes BSW testing on light vehicles, particularly at higher POV closing speeds, and for active safety systems (as discussed next), should encourage robust sensing system development, improving detection of other objects like motorcycles. However, the Agency has planned an upcoming research project addressing injuries and fatalities for other vulnerable road users, specifically motorcyclists. The Agency will continue observing BSW technology development and is likely to include motorcycle detection test procedures in NCAP later if the technology meets the four prerequisites.

Several commenters offered additional BSW test procedure expansion suggestions. MCW suggested adopting test scenarios for curved roads and low light conditions. CU proposed assessing whether BSW systems clearly indicate system non-operation to drivers, as sensors sometimes become inoperable in poor weather or when blocked.

As with all ADAS technologies, NHTSA recognizes the need to understand and assure BSW system crash mitigation performance in all practical real-world situations. However, comprehensive testing isn’t always practical within NCAP’s scope. For technologies meeting NCAP’s four inclusion principles, the Agency primarily attempted to address the most frequent, fatal, and injurious pre-crash scenarios when prioritizing tests. As ADAS technologies penetrate the fleet sufficiently, the Agency can evaluate real-world system performance and adjust performance criteria to address additional test conditions, like those suggested by MCW. Regarding CU’s suggestion, the Agency believes most vehicle manufacturers include malfunction indicators informing drivers when systems are inoperable due to sensor blockage or severe weather, based on vehicle owner’s manual reviews.

NHTSA also considered Bosch’s request to expand BSW definition to encourage longer detection distance systems. NHTSA believes, as discussed, using higher POV closing speeds to assess BSW performance may effectively drive enhanced blind spot system capabilities, like those for rearward-looking ADAS applications, such as BSI, or automatic lane change functions.

b. Test Procedure Harmonization

Several commenters suggested NHTSA harmonize its BSW test procedure with International Organization for Standardization (ISO) standard 17387:2008, Intelligent transport systems—Lane change decision aid systems (LCDAS)—Performance requirements and test procedures, or aspects of this standard. Global Automakers and Hyundai commented NHTSA should shift the forward blind zone edge rearward from rearview mirrors to the 95th percentile person’s eye point, as in ISO 17387. Hyundai stated the ISO procedure is designed so when the POV is in line with the SV driver’s eye ellipse, the driver’s peripheral vision allows POV visibility without BSW system assistance. ASC, Continental, and Subaru also suggested aligning warning zones in the Agency’s BSW test procedure with ISO 17387.

The Agency disagrees with commenters’ suggestion to adopt the ISO procedure for defining the forward blind zone edge using the eye ellipse of a 95th percentile person. NHTSA believes blind zones should be defined by vehicle characteristics, not a specific seated individual, as real-world blind spots differ depending on the driver’s size. People vary in size, seat positions, and seating preferences. For example, 95th percentile males will sit more rearward, and 5th percentile females more forward. Drivers also have personal side view mirror adjustment preferences, which may not be optimal or provide a full field of view when checking mirrors for lane changes. For these reasons, the Agency tentatively concludes setting the forward blind zone plane at the rearmost part of side view mirrors, as in its BSW test procedure, is more appropriate and safer for consumers. This approach should best accommodate various driver sizes and seating positions, while also reducing test complexity in blind zone definition.

2. Adding Blind Spot Intervention (BSI)

Blind spot intervention (BSI) systems, similar to AEB and LKS, actively intervene to help drivers avoid collisions. BSW systems alert drivers to vehicles in blind spots, while BSI systems activate when BSW alerts are ignored, intervening by automatically braking or steering vehicles back into unobstructed lanes. With their active capability, BSI systems can help drivers avoid collisions with vehicles approaching blind spots, in addition to preventing crashes with vehicles already in blind spots.

Like BSW systems, BSI systems use rear-facing sensors to detect vehicles next to or behind the vehicle in adjacent lanes. Depending on system design, BSI activation may or may not require driver turn signal operation during lane changes. Some BSI systems may only operate if the vehicle’s BSW system is also enabled.

As discussed, UMTRI found GM’s BSW system, Side Blind Zone Alert, produced a non-significant 3 percent lane change crash reduction. However, when combined with later generation Lane Change Alert technology, effectiveness increased to 26 percent[96]. Given BSI’s recent fleet penetration, NHTSA is unaware of effectiveness studies for this technology. However, as discussed, the Agency believes active safety technologies are more effective than warning technologies. The UMTRI study concluded AEB is more effective than FCW alone and LKS more effective than LDW. The Agency believes this relationship will likely hold for blind spot systems, with BSI being more effective than BSW alone. NHTSA also believes adopting ADAS technologies like BSI should encourage enhanced BSW system capabilities (motorcycle and bicycle detection) and may increase robustness of other ADAS applications.

NHTSA proposes using its published draft test procedure, “Blind Spot Intervention System Confirmation Test”[97], to evaluate BSI-equipped vehicle performance in NCAP. The Agency’s test procedure comprises three scenarios: Subject Vehicle (SV) Lane Change with Constant Headway, SV Lane Change with Closing Headway, and SV Lane Change with Constant Headway, False Positive Assessment. The first two scenarios involve SVs initiating or attempting lane changes into adjacent lanes while a single POV is in the SV’s blind zone (Scenario 1) or approaching from the rear (Scenario 2). The third scenario evaluates BSI system propensity for inappropriate activation in non-critical driving scenarios posing no safety risk to SV occupants. In each test, the POV is a strikeable object with compact passenger car characteristics. System performance requirements stipulate SVs must not contact POVs during any trial. NHTSA requests comment on the appropriate number of trials for each test. Each scenario, and proposed evaluation criteria, is detailed below[98]:

SV Lane Change with Constant Headway—The POV is driven at 72.4 kph (45 mph) in a lane adjacent and left of the SV, also at 72.4 kph (45 mph), with constant longitudinal offset so the POV’s front-most part is 1 m (3.3 ft.) ahead of the SV’s rear-most part. After steady-state driving, the SV driver engages the left turn signal at least 3 s after validity criteria are met. Within 1.0 ± 0.5 s after turn signal activation, the driver manually initiates a lane change into the POV’s lane, releasing the steering wheel within 250 ms of the SV exiting an 800.1 m (2,625 ft.) radius curve. To meet performance criteria, the BSI system must intervene to prevent the SV’s left rear from contacting the POV’s right front. Additionally, SV BSI intervention should not cause the SV to travel >0.3 m (1 ft.) beyond the lane line inboard edge separating the SV travel lane from the adjacent right lane within validity period.
SV Lane Change with Closing Headway Scenario—The POV is driven at a constant 80.5 kph (50 mph) towards the SV’s rear in an adjacent lane left of the SV, which is traveling at a constant 72.4 kph (45 mph). During testing, the SV driver engages turn signals when the POV is 4.9 ± 0.5 s from a vertical plane defined by the SV rear and perpendicular to the SV travel lane. Within 1.0 ± 0.5 s after turn signal activation, the driver manually initiates a lane change into the POV’s lane, releasing the steering wheel within 250 ms of the SV exiting an 800.1 m (2,625 ft.) radius curve. To meet performance criteria, the BSI system must intervene to prevent the SV’s left rear from contacting the POV’s right front. Additionally, SV BSI intervention should not cause the SV to travel >0.3 m (1 ft.) beyond the lane line inboard edge separating the SV travel lane from the adjacent right lane within validity period.
SV Lane Change with Constant Headway, False Positive Assessment Test—The POV is driven at 72.4 kph (45 mph) in a lane two lanes left of the SV’s initial travel lane, with constant longitudinal offset so the POV’s front-most part is 1 m (3.3 ft.) ahead of the SV’s rear-most part, also traveling at 72.4 kph (45 mph). The SV driver engages the left turn signal at least 3 s after pre-SV lane change test validity criteria are met. Within 1.0 ± 0.5 s after turn signal activation, the driver manually initiates a lane change into the left adjacent lane (between SV and POV). For this test, the driver does not release the steering wheel. Since the lane change will not result in SV-to-POV impact, the SV BSI system must not intervene during valid trials. To determine BSI intervention, SV yaw rate data during individual trials are compared to a baseline composite. After time-alignment to the baseline, data difference must not exceed 1 degree/second within the validity period.

Proposed crash-imminent BSI test scenarios represent pre-crash scenarios corresponding to a substantial portion of real-world lane change crash fatalities and injuries. As discussed in the BSW crash statistics section, Volpe showed ~28 percent of fatalities and 57 percent of injuries in lane change crashes occurred on roads with posted speeds of 72.4 kph (45 mph) or lower[99]. Furthermore, ~14 percent of fatalities and 24 percent of injuries were reported for crashes at known travel speeds of 72.4 kph (45 mph) or lower[100].

NHTSA has conducted a series of tests using its proposed BSI test procedure. As BSI systems are not widely available, the Agency selected vehicles to cover as many manufacturers as possible implementing this technology. All BSW-tested vehicles also underwent BSI testing. Test reports are available in the docket for this notice. For testing, the Agency used the Global Vehicle Target (GVT) Revision G to represent the POV, consistent with the BSI test procedure specifying a strikeable object[101]. When BSI technology assessment is incorporated into NCAP, the Agency plans to use the GVT Revision G as a strikeable target, consistent with Euro NCAP’s ADAS test procedures specifying strikeable targets. Regarding BSW and BSI technology testing in NCAP to address lane change crashes, NHTSA seeks comment on the following:

(16) Should all BSW testing be conducted without the turn signal indicator activated? Why or why not? If the Agency was to modify the BSW test procedure to stipulate activation of the turn signal indicator, should the test vehicle be required to provide an audible or haptic warning that another vehicle is in its blind zone, or is a visual warning sufficient? If a visual warning is sufficient, should it continually flash, at a minimum, to provide a distinction from the blind spot status when the turn signal is not in use? Why or why not?

(17) Is it appropriate for the Agency to use the Straight Lane Pass-by Test to quantify and ultimately differentiate a vehicle’s BSW capability based on its ability to provide acceptable warnings when the POV has entered the SV’s blind spot (as defined by the blind zone) for varying POV-SV speed differentials? Why or why not?

(18) Is using the GVT as the strikeable POV in the BSI test procedure appropriate? Is using Revision G in NCAP appropriate? Why or why not?

(19) The Agency recognizes that the BSW test procedure currently contains two test scenarios that have multiple test conditions (e.g., test speeds and POV approach directions (left and right side of the SV)). Is it necessary for the Agency to perform all test scenarios and test conditions to address the real-world safety problem adequately, or could it test only certain scenarios or conditions to minimize test burden in NCAP? For instance, should the Agency consider incorporating only the most challenging test conditions into NCAP, such as the ones with the greatest speed differential, or choose to perform the test conditions having the lowest and highest speeds? Should the Agency consider only performing the test conditions where the POV passes by the SV on the left side if the vehicle manufacturer provides test data to assure the left side pass-by tests are also representative of system performance during right side pass-by tests? Why or why not?

(20) Given the Agency’s concern about the amount of system performance testing under consideration in this RFC, it seeks input on whether to include a BSI false positive test. Is a false positive assessment needed to insure system robustness and high customer satisfaction? Why or why not?

(21) The BSW test procedure includes 7 repeated trials for each test condition (i.e., test speed and POV approach direction). Is this an appropriate number of repeat trials? Why or why not? What is the appropriate number of test trials to adopt for each BSI test scenario, and why? Also, what is an appropriate pass rate for each of the two tests, BSW and BSI, and why is it appropriate?

(22) Is it reasonable to perform only BSI tests in conjunction with activation of the turn signal? Why or why not? If the turn signal is not used, how can the operation of BSI be differentiated from the heading adjustments resulting from an LKS intervention? Should the SV’s LKS system be switched off during conduct of the Agency’s BSI evaluations? Why or why not?

C. Adding Pedestrian Automatic Emergency Braking (PAEB)

Another important ADAS technology NHTSA proposes for NCAP upgrade inclusion is pedestrian automatic emergency braking (PAEB). PAEB systems function similarly to AEB systems but detect pedestrians instead of vehicles. PAEB uses forward-looking sensor information to warn and actively brake when a pedestrian, or sometimes a cyclist, is in front of the vehicle and the driver has not acted to avoid impact. Similar to AEB, PAEB systems typically use cameras to determine pedestrian imminent danger, though some systems may use cameras, radar, lidar, and/or thermal imaging sensor combinations.

Many pedestrian crashes occur when pedestrians are in a vehicle’s forward path. Four common pedestrian crash scenarios include when vehicles are:

Heading straight and pedestrians are crossing the road;
Turning right and pedestrians are crossing the road;
Turning left and pedestrians are crossing the road; and
Heading straight and pedestrians are walking along or against traffic.

These four crash scenarios are defined as Scenarios S1-S4, respectively, by the Crash Avoidance Metrics Partnership (CAMP) Crash Imminent Braking (CIB) Consortium[102].

Two scenarios, S1 and S4, are included in NHTSA’s draft research PAEB test procedure, published November 21, 2019, and referred to as the 2019 PAEB test procedure[103]. The S1 scenario represents pedestrians crossing the road in front of vehicles, while S4 represents pedestrians moving with or against traffic along roadsides in vehicle paths. Both scenarios are repeated for multiple pedestrian impact locations. S1 and S4 were chosen for NHTSA’s 2019 PAEB test procedure because a 2011-2012 GES and FARS pedestrian crash data review[104] found these two pre-crash scenarios (S1 and S4) accounted for ~33,000 (52 percent) of vehicle-pedestrian crashes and 3,000 (90 percent) of fatal vehicle-pedestrian crashes with light vehicles striking pedestrians as the first event. Furthermore, these crashes accounted for 67 percent of MAIS 2+ and 76 percent of MAIS 3+ injured pedestrians[105]. The 2019 PAEB test procedure only considered daylight test conditions for both S1 and S4 scenarios.

The Agency’s 2019 PAEB test procedure excludes CAMP scenarios S2 (vehicle turning right, pedestrian crossing road) and S3 (vehicle turning left, pedestrian crossing road). In response to the December 2015 notice, several commenters stated addressing these scenarios with available technology may generate significant false positive detections, potentially causing hazardous situations (unexpected sudden braking while turning in traffic) leading drivers to disable PAEB systems or increase rear-end collisions. Commenters explained S2 and S3 scenarios require more sophisticated algorithms and robust test methodologies than S1 and S4. However, ZF TRW mentioned ADAS sensors designed to meet Euro NCAP’s Vulnerable Road Users test procedures would have increased fields of view (FOV), improving their effectiveness in turning scenarios. Others stated articulating mannequins may not represent real humans for all sensing technologies in turning scenarios. Most commenters indicated prioritizing scenarios with the most significant safety benefits (S1 and S4) was more appropriate. Commenters stated adding S2 and S3 scenarios would be more practical when technology matures. NHTSA will continue evaluating PAEB systems to assess the feasibility of expanding PAEB test suites as technology advances. The Agency will consider adding S2 and S3 scenarios to NCAP in the future once repeatable and reliable test data supports their inclusion.

In the 2019 PAEB test procedure, the S1 test scenario includes seven test conditions—S1a, S1b, S1c, S1d, S1e, S1f, and S1g. For these tests, SVs travel straight forward at 40 kph (24.9 mph). Additionally, SVs also travel at 16 kph (9.9 mph) for test conditions S1a, S1b, S1c, and S1d. Pedestrian mannequins cross perpendicular to the SV’s travel line at 5 kph (3.1 mph) for all conditions, except S1e, where mannequins cross at 8 kph (5.0 mph). In S1a, SVs encounter crossing adult pedestrian mannequins walking from the nearside (passenger’s side) with 25 percent vehicle overlap[106]. In S1b and S1c, SVs encounter crossing adult pedestrians walking from the nearside with 50 percent and 75 percent vehicle overlap, respectively. In S1d, SVs encounter crossing child pedestrian mannequins running from behind parked vehicles from the nearside with 50 percent vehicle overlap. In S1e, SVs encounter crossing adult pedestrians running from the offside (driver’s side) with 50 percent vehicle overlap. In S1f, SVs encounter crossing adult pedestrians walking from the nearside that stop short (−25% overlap) of entering the vehicle’s path. In S1g, SVs encounter crossing adult pedestrians walking from the nearside that clear the vehicle’s path (125% overlap).

The S4 test scenario in the 2019 PAEB test procedure includes three test conditions—S4a, S4b, and S4c. In this scenario, SVs travel straight forward at 40 kph (24.9 mph) and/or 16 kph (9.9 mph) (for S4a and S4b) and pedestrian mannequins move parallel to traffic flow at 5 kph (3.1 mph) (for S4c) or are stationary (for S4a and S4b) in front of SVs. For all S4 test conditions, SVs are aligned to impact pedestrians at 25 percent overlap. In S4a, SVs encounter adult pedestrians standing ahead on the nearside facing away from approaching SVs. In S4b, SVs encounter adult pedestrians standing ahead on the nearside facing towards approaching SVs. In S4c, SVs encounter adult pedestrians walking ahead on the nearside facing away from approaching SVs.

The Agency proposes several changes to the 2019 PAEB test procedure for NCAP adoption. These changes involve pedestrian mannequins, test speeds and included test conditions, lighting conditions, and the number of test trials per test condition.

The first proposed change concerns pedestrian targets. As recommended by commenters responding to the December 2015 notice, the Agency proposes using state-of-the-art mannequins with articulated, moving legs, instead of posable child and adult pedestrian test mannequins from the 2019 PAEB test procedure. NHTSA believes articulating pedestrian targets are more representative of walking pedestrians and expects these more realistic targets will encourage PAEB system development that more accurately and effectively detects, classifies, and responds to pedestrians. This should allow manufacturers to improve current PAEB system effectiveness. The Agency also recognizes adopting child and adult articulating targets would harmonize with other major consumer information-focused entities using articulating mannequins, like Euro NCAP and IIHS. The Bipartisan Infrastructure Law mandated NHTSA identify NCAP harmonization opportunities with third-party safety rating programs, and pedestrian mannequins represent one such opportunity.

The second proposed change to the 2019 PAEB test procedure for NCAP incorporation involves test speeds. Test speeds in the 2019 PAEB test procedure correspond to a relatively small percentage of pedestrian injury and fatality crashes. Volpe’s 2011-2015 FARS and GES data analysis showed 9 percent of pedestrian fatalities and 25 percent of pedestrian injuries resulted from crashes on roads with posted speeds of 40.2 kph (25 mph) or less, while 88 percent of fatalities and 43 percent of injuries occurred for crashes on roads with posted speeds over 40.2 kph (25 mph)[107 [108]. For crashes on roads with known travel speeds, 6 percent of pedestrian fatalities and 19 percent of injuries were reported for travel speeds of 40.2 kph (25 mph) or less, while 36 percent of fatalities and 7 percent of injuries occurred for travel speeds over 40.2 kph (25 mph)[109]. NHTSA notes speeding was a factor in only 5 percent of fatal pedestrian crashes, suggesting posted speed could closely correlate with vehicle travel speed before pedestrian impact[110 [111].

As Volpe’s analysis focused on 2011-2015 FARS and GES data, most studied vehicles likely lacked PAEB systems. Recently, IIHS studied ~1,500 police-reported crashes involving various 2017-2020 model year vehicles from various manufacturers to examine PAEB system effects on real-world pedestrian crashes[112]. The Institute found “pedestrian AEB associated with a 32 percent pedestrian crash odds reduction on roads with ≤25 mph speed limits and 34 percent reduction on 30-35 mph limits, but no reduction at all on roads with ≥50 mph limits…”. These findings highlight current PAEB system limitations and the importance of adopting higher PAEB test speeds (where feasible) to encourage further safety improvement.

To establish feasible speed thresholds for PAEB test procedure adoption, the Agency tested a selection of MY 2020 vehicles from various manufacturers to assess current PAEB system operational range and performance. Vehicles were selected to cover a range of makes, types, sizes, global and domestic products, and forward-facing sensor types (camera-only, stereo camera, fused camera plus radar, etc.) per manufacturer and across all manufacturers.

For this study, the Agency used the 2019 PAEB test procedure but employed articulating mannequins instead of posable mannequins and expanded test procedure specifications to include increased vehicle test speeds for S1b, S1d, S1e, S4a, and S4c test conditions. For these tests, SV speed was incrementally increased to identify when each SV reached operational limits and did not respond to pedestrian targets. Maximum test speeds for S1 and S4 scenarios were set to 60 kph (37.2 mph) and 80 kph (49.7 mph), respectively, before tests began[113]. These maximum speeds are consistent with Euro NCAP’s AEB Vulnerable Road User test protocol and correspond to up to 74 percent of fatal pedestrian crashes and 65 percent of injurious pedestrian crashes on U.S. roadways, per Volpe’s 2011-2015 FARS and GES posted speed data analysis[114]. When no or late intervention occurred for a vehicle and test condition (test scenario and speed combination), NHTSA repeated the test condition at a 5 kph (3.1 mph) lower test speed. This reduced speed defined the system’s upper capabilities.

A test matrix of the PAEB characterization study regarding test speed is provided below.

Full PAEB test series (includes S1 a-g and S4 a-c)

Daytime light conditions, articulating dummies, and additional SV test speeds in kph (mph) for S1b, d, and e, and S4a and c, as shown in Table 4.

Table 4—Complete Matrix of the PAEB Characterization Study
| Scenario | S1a | S1b | S1c | S1d | S1e | S1f | S1g | S4a | S4b | S4c |
|—|—|—|—|—|—|—|—|—|—|—|
| Subject Vehicle Speed (kph/mph) | 16.0/9.9 40.0/24.9 | 16.0/9.9 20.0/12.4 | 16.0/9.9 40.0/24.9 | 16.0/9.9 20.0/12.4 | 40.0/24.9 50.0/31.1 | 40.0/24.9 | 40.0/24.9 | 16.0/9.9 40.0/24.9 | 16.0/9.9 40.0/24.9 | 16.0/9.9 40.0/24.9 |
| | 30.0/18.6 | 30.0/18.6 | 60.0/37.3 | 50.0/31.1 | 50.0/31.1 |
| | 40.0/24.9 | 40.0/24.9 | 60.0/37.3 | 60.0/37.3 |
| | 50.0/31.1 | 50.0/31.1 | 70.0/43.5 | 70.0/43.5 |
| | 60.0/37.3 | 60.0/37.3 | 80.0/49.7 | 80.0/49.7 |

The Agency’s characterization testing showed many MY 2020 vehicles could repeatedly avoid impacting pedestrian mannequins at higher test speeds than in the 2019 PAEB test procedure. Several vehicles repeatedly achieved full crash avoidance at speeds up to 60 kph (37.3 mph) or higher for assessed S1 and S4 test conditions. Test reports are in the docket for this notice.

Based on these results, NHTSA proposes increasing maximum SV test speed from 40 kph (24.9 mph) in the 2019 PAEB test procedure to 60 kph (37.3 mph) for all PAEB test conditions proposed for NCAP (S1a-e and S4a-c). The Agency is not proposing to include PAEB false positive test conditions (S1f and S1g) in NCAP at this time but requests comment on this omission’s appropriateness. NHTSA notes 60 kph (37.3 mph) is the maximum vehicle speed Euro NCAP uses to assess PAEB performance for test conditions similar or identical to some proposed for NCAP, namely S1a, c, d, and e, and S4c. Adopting this higher speed will also drive improved PAEB system performance to address a larger portion of real-world fatalities and injuries.

The Agency also proposes a minimum 10 kph (6.2 mph) test speed for all proposed scenarios. While lower than the 2019 PAEB test procedure and characterization testing minimum speed (16 kph (9.9 mph)), it aligns with Euro NCAP’s pedestrian tests minimum speed, except for Euro NCAP’s Car-to-Pedestrian Longitudinal Adult (CPLA) scenario. CPLA scenario minimum vehicle test speed, similar to the Agency’s PAEB S4c, is 20 kph (12.4 mph)[115]. In accordance with the Bipartisan Infrastructure Law, the Agency is harmonizing with existing consumer information rating programs where possible and appropriate. NHTSA also believes reducing minimum test speed to 10 kph (6.2 mph) will ensure PAEB system functionality for crashes that can still cause injuries.

To harmonize with other consumer information programs on vehicle safety, NHTSA also proposes adopting Euro NCAP’s approach to assessing vehicle PAEB system performance by incrementally increasing SV speed from minimum to maximum test speeds for given scenarios. The Agency proposes 10 kph (6.2 mph) increments for speed progression. In December 2015 notice comments, Global Automakers and Mobileye encouraged NHTSA to expand PAEB test applicability, particularly S1, to include a broader speed range, as pedestrian injuries occur across crash speeds, as the Agency also indicated. The organizations also mentioned PAEB system performance reflects FOV and collision speed/detection distance trade-offs. Narrow FOV systems are more effective at higher speed crashes due to further sight range, and wider FOV systems are more effective at lower speed impacts.

As its third 2019 PAEB test procedure change, the Agency proposes expanding PAEB evaluation to include different lighting conditions. NHTSA’s PAEB characterization study included performance assessments for dark lighting conditions (nighttime testing) alongside daylight conditions in the 2019 PAEB test procedure for the same test vehicles. For each vehicle model tested, one test set was conducted with pedestrian mannequins illuminated only by vehicle lower beams, and another set with mannequins illuminated by upper beams. The mannequin area received no additional (external) light source. This repeat testing was done because Volpe’s 2011-2015 FARS data set showed 36 percent of pedestrian fatalities occurred in darkness without overhead lights. PAEB characterization study test matrices for dark lighting conditions are in Tables 5 and 6.

PAEB test series (includes S1b, d, and e, and S4a and c)

Dark conditions with lower beams, articulating dummies, and additional SV test speeds in kph (mph), are shown in Table 5.

Table 5—PAEB Test Series for Dark Conditions With Lower Beams
| Scenario | S1b | S1d | S1e | S4a | S4c |
|—|—|—|—|—|—|
| Subject Vehicle Speed (kph/mph) | 16.0/9.9 | 16.0/9.9 | 40.0/24.9 | 16.0/9.9 | 16.0/9.9 |
| | 20.0/12.4 | 20.0/12.4 | 50.0/31.1 | 40.0/24.9 | 40.0/24.9 |
| | 30.0/18.6 | 30.0/18.6 | 60.0/37.3 | 50.0/31.1 | 50.0/31.1 |
| | 40.0/24.9 | 40.0/24.9 | 60.0/37.3 | 60.0/37.3 |
| | 50.0/31.1 | 50.0/31.1 | 70.0/43.5 | 70.0/43.5 |
| | 60.0/37.3 | 60.0/37.3 | 80.0/49.7 | 80.0/49.7 |

PAEB test series (includes S1b, d, and e, and S4a and c)

Dark conditions with upper beams, articulating dummies, and additional SV test speeds in kph (mph), are shown in Table 6.

Table 6—PAEB Test Series for Dark Conditions With Upper Beams
| Scenario | S1b | S1d | S1e | S4a | S4c |
|—|—|—|—|—|—|
| Subject Vehicle Speed (kph/mph) | 16.0/9.9 | 16.0/9.9 | 40.0/24.9 | 16.0/9.9 | 16.0/9.9 |
| | 20.0/12.4 | 20.0/12.4 | 50.0/31.1 | 40.0/24.9 | 40.0/24.9 |
| | 30.0/18.6 | 30.0/18.6 | 60.0/37.3 | 50.0/31.1 | 50.0/31.1 |
| | 40.0/24.9 | 40.0/24.9 | 60.0/37.3 | 60.0/37.3 |
| | 50.0/31.1 | 50.0/31.1 | 70.0/43.5 | 70.0/43.5 |
| | 60.0/37.3 | 60.0/37.3 | 80.0/49.7 | 80.0/49.7 |

Agency characterization testing (Tables 5 and 6) revealed PAEB system performance generally degraded in dark conditions versus daylight. Certain test conditions, like S1d and S1e, were particularly challenging in darkness, especially with vehicle lower beams. However, a few vehicles repeatedly avoided pedestrian mannequin contact at speeds up to 60 kph (37.3 mph) for certain test conditions using only lower beams.

NHTSA’s findings for PAEB system performance during testing align generally with IIHS’ recent 2017-2020 model year vehicle system effectiveness study. IIHS found while PAEB systems were associated with a 32 percent pedestrian crash reduction in daylight and a 33 percent reduction in artificially lit areas during dawn, dusk, or night, there was no evidence of PAEB system effectiveness at nighttime without street lighting[116].

Based on PAEB characterization study results and IIHS findings, NHTSA proposes performing proposed test conditions (S1 a-e and S4 a-c) under daylight and dark conditions with vehicle lower beams. NHTSA notes Euro NCAP conducts PAEB testing similar to Agency S4c under dark conditions with vehicle upper beams. As the Agency cannot ensure vehicle upper beam usage during real-world nighttime driving, NHTSA proposes nighttime PAEB assessments using only lower beams for all test conditions included in NCAP at this time. However, if SVs have advanced lighting systems like semiautomatic headlamp beam switching and/or adaptive driving beam head lighting systems, they should be enabled to automatically engage during nighttime PAEB assessments. The Agency believes this covers extreme light conditions, and performance with upper beams or infrastructure lighting can be reasonably inferred.

The Agency recognizes Euro NCAP performs testing similar to S1a and S1c at 10 kph (6.2 mph) to 60 kph (37.3 mph) in dark conditions with SV lower beams and overhead streetlights as additional light sources. To study potential performance differences from overhead lights in dark conditions, NHTSA performed additional testing for PAEB scenarios S1 b, d, and e and S4 a and c for a subset of test speeds (16 kph (9.9 mph) and 40 kph (24.9 mph)) for two MY 2020 vehicles used in its initial characterization study. This study used vehicle lower beams under dark conditions with overhead lights. For this limited testing, the Agency observed slightly better PAEB performance in dark lighting conditions with overhead lights than without.

NHTSA believes testing with vehicle lower beams in dark conditions without overhead lights is appropriate, particularly at higher speeds, as it assures system performance in real-world limited visibility situations. Furthermore, as previously noted, dark lighting conditions without overhead lights represented 36 percent of pedestrian fatalities, and dark lighting with overhead lights represented 39 percent in Volpe’s 2011-2015 FARS data set. Additionally, PAEB systems meeting performance specifications under dark conditions without overhead lights are likely to meet specifications under dark conditions with overhead lights. Thus, the Agency believes PAEB system assessments under dark conditions without overhead lights and with vehicle lower beams will encourage manufacturers to make design improvements addressing a significant portion of crashes currently causing pedestrian fatalities.

For PAEB performance criteria, NHTSA proposes vehicles achieve complete crash avoidance (no pedestrian mannequin contact) to pass trials at each specified test speed (10, 20, 30, 40, 50, and 60 kph (6.2, 12.4, 18.6, 24.9, 31.1, and 37.3 mph)) for each test condition (S1a-e and S4a-c). NHTSA believes this approach, combined with incremental SV speed increases, should limit pedestrian mannequin and SV damage during testing.

Along these lines, NHTSA proposes a fourth 2019 PAEB test procedure change regarding the number of test trials per test condition and speed combination. The 2019 PAEB test procedure specifies seven trials per test speed under each test condition. The Agency proposes not requiring more than one test per test speed and test condition combination if criteria are met, and proposes the pass rate for a given test speed depend on whether additional trials are needed[117].

For a given test condition, the test sequence starts at the 10 kph (6.2 mph) minimum speed. To pass, tests must be valid (specifications and tolerances met), and SVs must not contact pedestrian mannequins. If SVs do not contact mannequins in the first valid test, test speed incrementally increases by 10 kph (6.2 mph), and the next test in sequence is performed. Unless SVs contact mannequins, this iterative process continues until a maximum 60 kph (37.3 mph) test speed is evaluated. If SVs contact mannequins, and relative longitudinal velocity between SVs and mannequins is ≤50 percent of initial SV speed, the Agency performs four additional (repeated) tests at the same speed where impact occurred. Vehicles must not contact mannequins for at least three of five tests at that speed to pass that test condition and speed combination[118]. If SVs contact mannequins during valid tests (whether the first test at a speed or subsequent trial at that speed), and relative impact velocity exceeds 50 percent of initial SV speed, no additional tests are done at that speed and condition, and SVs fail the test condition at that speed.

The Agency is pursuing a PAEB system assessment approach differing from evaluation criteria proposed for the other four ADAS technologies to reduce test burden while ensuring passing systems have robust designs offering enhanced safety. NHTSA recognizes proposing a large number of PAEB test conditions for NCAP inclusion—eight total. The Agency also acknowledges these test conditions must be repeated for multiple test speeds and lighting conditions, inherently increasing test burden. Therefore, the Agency believes reducing test trials required at a given speed for a particular test condition is reasonable, as SV PAEB systems will also be assessed at subsequent speeds, supporting system robustness. This is further supported by the Agency’s proposal to require five trials when SVs fail to meet no contact performance in initial valid trials for test condition and speed combinations.

While NHTSA believes the proposed PAEB system assessment approach is most reasonable, the Agency requests comment on whether to pursue an alternative, such as conducting seven trials per test condition and speed combination, and requiring five of seven trials to meet the no contact performance criterion. This latter approach would be similar to that proposed for the other ADAS technologies discussed earlier.

Previously, NHTSA noted it did not conduct S2 and S3 test scenarios in the characterization study and is not proposing these for this proposal. The Agency agrees with prior comments that most U.S. fleet vehicles lack sensing systems detecting pedestrians while turning due to insufficient FOV. The American Automobile Association (AAA)[119] recently conducted PAEB tests, including an S2 scenario with right-turning vehicles and crossing adult pedestrians. PAEB systems in four 2019 model year vehicles tested did not react to targets during a scenario similar to NHTSA’s S2, resulting in all test vehicles colliding with pedestrian targets. These systems performed better in scenarios similar to NHTSA’s S1; however, vehicles avoided pedestrian target collisions 40 percent of the time at 32.2 kph (20 mph) and nearly all the time at 48.3 kph (30 mph). Furthermore, in its recent PAEB system effectiveness study, IIHS found while AEB with pedestrian detection was associated with significant pedestrian crash risk (~27 percent) and injury crash risk (~30 percent) reductions, no evidence suggested existing systems were effective while PAEB-equipped vehicles were turning[120]. Considering these findings, NHTSA believes focusing efforts on higher-speed PAEB testing with various lighting conditions using proposed S1 and S4 test scenarios is more beneficial at this time.

Regarding the NCAP PAEB testing program, NHTSA seeks comment on the following:

(23) Is the proposed test speed range, 10 kph (6.2 mph) to 60 kph (37.3 mph), to be assessed in 10 kph (6.2 mph) increments, most appropriate for PAEB test scenarios S1 and S4? Why or why not?

(24) The Agency has proposed to include Scenarios S1 a-e and S4 a-c in its NCAP assessment. Is it necessary for the Agency to perform all test scenarios and test conditions proposed in this RFC notice to address the safety problem adequately, or could NCAP test only certain scenarios or conditions to minimize test burden but still address an adequate proportion of the safety problem? Why or why not? If it is not necessary for the Agency to perform all test scenarios or test conditions, which scenarios/conditions should be assessed? Although they are not currently proposed for inclusion, should the Agency also adopt the false positive test conditions, S1f and S1g? Why or why not?

(25) Given that a large portion of pedestrian fatalities and injuries occur under dark lighting conditions, the Agency has proposed to perform testing for the included test conditions (i.e., S1 a-e and S4 a-c) under dark lighting conditions (i.e., nighttime) in addition to daylight test conditions for test speed range 10 kph (6.2 mph) to 60 kph (37.3 mph). NHTSA proposes that a vehicle’s lower beams would provide the source of light during the nighttime assessments. However, if the SV is equipped with advanced lighting systems such as semiautomatic headlamp beam switching and/or adaptive driving beam head lighting system, they shall be enabled to automatically engage during the nighttime PAEB assessment. Is this testing approach appropriate? Why or why not? Should the Agency conduct PAEB evaluation tests with only the vehicle’s lower beams and disable or not use any other advanced lighting systems?

(26) Should the Agency consider performing PAEB testing under dark conditions with a vehicle’s upper beams as a light source? If yes, should this lighting condition be assessed in addition to the proposed dark test condition, which would utilize only a vehicle’s lower beams along with any advanced lighting system enabled to automatically engage, or in lieu of the proposed dark testing condition? Should the Agency also evaluate PAEB performance in dark lighting conditions with overhead lights? Why or why not? What test scenarios, conditions, and speed(s) are appropriate for nighttime (i.e., dark lighting conditions) testing in NCAP, and why?

(27) To reduce test burden in NCAP, the Agency proposed to perform one test per test speed until contact occurs, or until the vehicle’s relative impact velocity exceeds 50 percent of the initial speed of the subject vehicle for the given test condition. If contact occurs and if the vehicle’s relative impact velocity is less than or equal to 50 percent of the initial SV speed for the given combination of test speed and test condition, an additional four test trials will be conducted at the given test speed and test condition, and the SV must meet the passing performance criterion (i.e., no contact) for at least three out of those five test trials in order to be assessed at the next incremental test speed. Is this an appropriate approach to assess PAEB system performance in NCAP, or should a certain number of test trials be required for each assessed test speed? Why or why not? If a certain number of repeat tests is more appropriate, how many test trials should be conducted, and why?

(28) Is a performance criterion of “no contact” appropriate for the proposed PAEB test conditions? Why or why not? Alternatively, should the Agency require minimum speed reductions or specify a maximum allowable SV-to-mannequin impact speed for any or all of the proposed test conditions (i.e., test scenario and test speed combination)? If yes, why, and for which test conditions? For those test conditions, what speed reductions would be appropriate? Alternatively, what maximum allowable impact speed would be appropriate?

(29) If the SV contacts the pedestrian mannequin during the initial trial for a given test condition and test speed combination, NHTSA proposes to conduct additional test trials only if the relative impact velocity observed during that trial is less than or equal to 50 percent of the initial speed of the SV. For a test speed of 60 kph (37.3 mph), this maximum relative impact velocity is nominally 30 kph (18.6 mph), and for a test speed of 10 kph (6.2 mph), the maximum relative impact velocity is nominally 5 kph (3.1 mph). Is this an appropriate limit on the maximum relative impact velocity for the proposed range of test speeds? If not, why? Note that the tests in Global Technical Regulation (GTR) No. 9 for pedestrian crashworthiness protection simulates a pedestrian impact at 40 kph (24.9 mph).

(30) For each lighting condition, the Agency is proposing 6 test speeds (i.e., those performed from 10 to 60 kph (6.2 to 37.3 mph) in increments of 10 kph (6.2 mph)) for each of the 8 proposed test conditions (S1a, b, c, d, and e and S4a, b, and c). This results in a total of 48 unique combinations of test conditions and test speeds to be evaluated per lighting condition, or 96 total combinations for both light conditions. The Agency mentions later, in the ADAS Ratings System section, that it plans to use check marks, as is done currently, to give credit to vehicles that (1) are equipped with the recommended ADAS technologies, and (2) pass the applicable system performance test requirements for each ADAS technology included in NCAP until it issues (1) a final decision notice announcing the new ADAS rating system and (2) a final rule to amend the safety rating section of the vehicle window sticker (Monroney label). For the purposes of providing credit for a technology using check marks, what is an appropriate minimum overall pass rate for PAEB performance evaluation? For example, should a vehicle be said to meet the PAEB performance requirements if it passes two-thirds of the 96 unique combinations of test conditions and test speeds for the two lighting conditions (i.e., passes 64 unique combinations of test conditions and test speeds)?

(31) Given previous support from commenters to include S2 and S3 scenarios in the program at some point in the future and the results of AAA’s testing for one of the turning conditions, NHTSA seeks comment on an appropriate timeframe for including S2 and S3 scenarios into the Agency’s NCAP. Also, NHTSA requests from vehicle manufacturers information on any currently available models designed to address, and ideally achieve crash avoidance during conduct of, the S2 and S3 scenarios to support Agency evaluation for a future program upgrade.

(32) Should the Agency adopt the articulated mannequins into the PAEB test procedure as proposed? Why or why not?

(33) In addition to tests performed under daylight conditions, the Agency is proposing to evaluate the performance of PAEB systems during nighttime conditions where a large percentage of real-world pedestrian fatalities occur. Are there other technologies and information available to the public that the Agency can evaluate under nighttime conditions?

(34) Are there other safety areas that NHTSA should consider as part of this or a future upgrade for pedestrian protection?

(35) Are there any aspects of NCAP’s proposed PAEB test procedure that need further refinement or clarification before adoption? If so, what additional refinement or clarification is necessary, and why?

(36) Considering not only the increasing number of cyclists killed on U.S. roads but also the limitations of current AEB systems in detecting cyclists, the Agency seeks comment on the appropriate timeframe for adding a cyclist component to NCAP and requests from vehicle manufacturers information on any currently available models that have the capability to validate the cyclist target and test procedures used by Euro NCAP to support evaluation for a future NCAP program upgrade.

(37) In addition to the test procedures used by Euro NCAP, are there others that NHTSA should consider to address the cyclist crash population in the U.S. and effectiveness of systems?

D. Updating Forward Collision Prevention Technologies

As mentioned, NHTSA will retain current ADAS technologies (forward collision warning, crash imminent braking, and dynamic brake support) designed to address forward collisions (rear-end crashes) in NCAP’s crash avoidance program. As discussed in NHTSA’s March 2019 study, these technologies can prevent or mitigate eight rear-end pre-crash scenarios, averaging ~1.70 million annual crashes, 29.4 percent of all U.S. crashes. As shown in Table A-1, these crashes resulted in ~1,275 annual fatalities and 883,386 MAIS 1-5 injuries, 3.8 percent of fatalities and 31.5 percent of injuries[123].

FCW technology evaluations were introduced into NCAP starting with model year 2011 vehicles[124], while CIB and DBS systems (AEB) were added starting with model year 2018 vehicles[125]. These technologies are not standard on all passenger vehicles, so NCAP recommendation and shopper information remains important. Further, NHTSA observed performance test failures for each technology during NCAP’s model year 2019 vehicle performance verification testing[126], so NCAP should continue informing shoppers of systems performing to NHTSA’s benchmark. Nevertheless, as discussed below, NHTSA sees opportunities to update current NCAP performance requirements for these three technologies.

1. Forward Collision Warning (FCW)

FCW systems are ADAS technologies monitoring vehicle speed, preceding vehicle speed, and inter-vehicle distance. If the distance to the vehicle ahead is too short and closing velocity too high, the FCW system warns drivers of impending rear-end collisions.

FCW systems typically have two components: a sensing system (radar, lidar, cameras, or combinations) detecting vehicles ahead and a warning system alerting drivers to potential crash threats (visual display, audible signal, and/or haptic signal). FCW alerts warn drivers of impending crashes so they can manually intervene (brake or steer evasively) to avoid or mitigate crashes.

NCAP’s current FCW test procedure[127] has three scenarios simulating frequent rear-end crash types: Lead vehicle stopped (LVS), lead vehicle decelerating (LVD), and lead vehicle moving (LVM) scenarios. In each scenario, the evaluated vehicle is the SV, and the vehicle ahead, a production mid-size passenger car, is the POV. Time-to-collision (TTC) criteria for each scenario represent the time needed for drivers to perceive impending rear-end crashes, decide corrective action, and respond with mitigation. TTC for each scenario is calculated by considering SV speed relative to POV speed upon FCW alert. If FCW systems fail to alert within the required time during testing, professional test drivers brake or steer to avoid collisions. A short description of each test scenario and passing result requirements based on TTC follows:

LVS—The SV encounters a stopped POV on a straight road. The SV moves at 72.4 kph (45 mph), and the POV is stationary. To pass, the SV must issue an FCW alert when TTC is at least 2.1 s.
LVD—The SV encounters a POV slowing with constant deceleration ahead on a straight road. The SV and POV both travel at 72.4 kph (45 mph) with 30.0 m (98.4 ft.) initial headway. The POV then decelerates, braking at a constant 0.3g deceleration in front of the SV. To pass, the SV must issue an FCW alert when TTC is at least 2.4 s.
LVM—The SV encounters a slower-moving POV directly ahead on a straight road. The SV and POV travel at constant speeds of 72.4 kph (45 mph) and 32.2 kph (20 mph), respectively. To pass, the SV must issue an FCW alert when TTC is at least 2.0 s.

Each scenario is conducted up to seven times. To meet NCAP system performance criteria, SVs must pass at least five of seven trials[128] for each of the three test scenarios.

NCAP’s FCW test scenarios directly relate to real-world crash data. 2011-2015 FARS and GES data analysis showed crashes analogous to the LVS test scenario, struck vehicles stopped at impact, occurred in 65 percent of rear-end crashes studied[129]. The LVD scenario, struck vehicle decelerating at impact, occurred in 22 percent of rear-end crashes, and the LVM scenario, struck vehicle moving at constant slower speed than the striking vehicle at impact, occurred in 10 percent of rear-end crashes. Collectively, these scenarios represented 97 percent of rear-end crashes. Regarding test speed, Volpe’s 2011-2015 FARS and GES data review concluded 28 percent of fatal rear-end crashes and 63 percent of all rear-end crashes occurred on roads with posted speed limits of 72.4 kph (45 mph) or less.

Currently, NHTSA credits vehicles equipped with FCW systems providing visual, audible, and/or haptic alerts meeting TTC requirements on its website with check marks. However, Agency research showed audible warnings in medium or high urgency situations significantly reduced crash severity relative to visual and tactile (haptic) warnings, which did not differ[130]. However, in a large-scale field test of FCW and LDW systems on 2013 Chevrolet and Cadillac models, the University of Michigan Transportation Research Institute (UMTRI) and GM found GM’s Safety Alert Seat, providing haptic seat vibration pulses, increased driver acceptance of FCW and LDW systems compared to audible alerts[131]. The study concluded FCW systems were turned off 6 percent of the time when Safety Alert Seats were selected (versus audible alerts), compared to 17 percent of the time with only audible alerts available. Given these findings, the Agency seeks comment on whether to credit vehicles equipped with LDW systems that provide a passing alert, regardless of alert type. Are there any LDW alert modalities, such as visual-only warnings, that the Agency should not consider acceptable when determining whether a vehicle meets NCAP’s performance test criteria? Should the Agency consider only certain alert modalities (such as haptic warnings) because they are more effective at re-engaging the driver and/or have higher consumer acceptance? NHTSA also seeks comment on whether to stop crediting FCW-equipped vehicles offering only visual FCW alerts[132].

NCAP’s current FCW test procedure states if FCW systems provide driver warning timing adjustment settings, at least one timing setting must meet procedure-specified TTC warning criteria. Therefore, if vehicles have warning timing adjustments, only the most conservative (earliest) warning setting is tested. Testing the most conservative setting is beneficial for track testing, where SV drivers must steer and/or brake to avoid POV crashes after FCW alerts. However, the Agency is concerned many consumers may not adjust FCW alert timing settings. Furthermore, consumers who adjust alert timing may be unlikely to select the earliest setting, as this setting is most likely to cause false positive alerts (nuisance alerts) during real-world operation[133]. The Agency recognizes the earliest FCW setting can be used to pass NCAP tests—allowing vehicles to gain NCAP credit even if they wouldn’t otherwise earn credit if later warning settings were tested. Thus, testing the earliest timing adjustment setting may make the Agency’s FCW performance assessment unrepresentative of many driver real-world experiences.

This concern was previously addressed in NHTSA’s 2015 AEB final decision notice, but the Agency has not updated its FCW test procedure since[134]. In that notice, the Agency stated NCAP, a consumer information program, should test vehicles as delivered, using factory default FCW warning adjustment settings for FCW and AEB testing, including PAEB. While the Agency still sees merit in testing default settings, NHTSA tentatively believes testing middle alert settings may be more appropriate. Testing middle or next latest alert settings would harmonize with Euro NCAP’s AEB Car-to-Car systems test protocol, potentially reducing manufacturer costs and ensuring consumers in both U.S. and European markets benefit from similar FCW system settings[135]. Harmonization was a common theme among commenters responding to NCAP’s December 2015 notice, with most manufacturers, suppliers, and industry groups requesting NHTSA harmonize test procedures, targets, and requirements with other global NCAPs, particularly Euro NCAP. As mentioned, the Bipartisan Infrastructure Law also required NHTSA to consider harmonization with third-party safety rating programs where possible. Given these considerations, the Agency proposes testing the middle (or next latest) FCW system setting, rather than default settings, when performing FCW, CIB, DBS, and PAEB NCAP tests on vehicles offering multiple FCW timing adjustment settings.

FCW systems are recognized as first-generation ADAS technologies designed to help drivers avoid impending rear-end collisions. In 2008, when NHTSA decided to include ADAS in NCAP, FCW was selected because the Agency believed (1) the technology addressed a major crash problem; (2) LDW system design had the potential to mitigate the crash problem; (3) safety benefits were projected; and (4) test procedures and evaluation criteria were available to ensure acceptable performance levels[136]. At the time, the Agency estimated FCW systems were 15 percent effective in preventing rear-end crashes. More recently, a 2017 IIHS study[137] found FCW systems may be more effective than NHTSA’s initial estimates, reducing rear-end crashes by 27 percent. Moreover, consumers have shown favorable system acceptance. In a 2019 Consumer Reports survey of over 57,000 subscribers, 69 percent of vehicle owners reported FCW technology satisfaction, 38 percent said it helped avoid crashes, and 54 percent trusted the system to work every time[138]. Positive consumer acceptance and improved system performance over time have increased fitment rates. As mentioned, <0.2 percent of model year 2011 vehicles were equipped with FCW systems, compared to 38.3 percent of model year 2018 vehicles.

One FCW system limitation is that they warn drivers, but do not provide significant automatic vehicle braking (some FCW systems use haptic brake pulses to alert drivers of crash-imminent situations, but they are not intended to effectively slow vehicles). Since NCAP included FCW systems, active safety systems with automatic braking (AEB) have entered the market. In a recent GM-sponsored study[139] evaluating ADAS technology real-world effectiveness (including FCW and AEB) on 3.8 million 2013-2017 GM vehicles, UMTRI found camera-based FCW systems produced an estimated 21 percent reduction in rear-end striking crashes, while studied AEB systems (camera-only, radar-only, and fused camera-radar systems) produced an estimated 46 percent reduction in the same crash type[140]. Similarly, a 2017 IIHS study found vehicles equipped with FCW and AEB showed a 50 percent reduction for the same crash type[141]. NHTSA draws from these research studies generally, since each has limitations and deviations from how NHTSA might evaluate fleet-wide[142] system effectiveness.

Functionally, research suggests active braking systems like AEB offer greater safety benefits than warning systems like FCW. However, NHTSA has found current AEB systems often integrate FCW and AEB functionalities into one frontal crash prevention system for improved real-world safety performance and high consumer acceptance. Consequently, the Agency believes this system integration may have NCAP FCW testing implications because current NCAP FCW requirements were developed when FCW and AEB functionalities were not always linked. As detailed later, NHTSA believes FCW could now be considered an AEB component and FCW operation evaluated using NCAP’s AEB and PAEB tests.

2. Automatic Emergency Braking (AEB)

To further address rear-end crashes, in November 2015, NHTSA published a final decision notice adding two AEB technologies, CIB and DBS, to NCAP, effective for model year 2018 vehicles[143].

Unlike FCW systems, AEB systems (CIB and DBS) are designed to actively help drivers avoid or mitigate rear-end crash severity. CIB systems provide automatic braking when forward-looking sensors indicate imminent crashes and drivers haven’t braked, while DBS systems provide supplemental braking when sensors determine driver-applied braking is insufficient to avoid imminent crashes.

Consumer Reports’ 2019 subscriber survey found 81 percent of vehicle owners satisfied with AEB technology, 54 percent said it helped avoid crashes, and 61 percent trusted the system to work every time[144]. Furthermore, IIHS’s 2017 study found rear-end collisions decreased by 50 percent for vehicles with AEB and FCW[145]. Similarly, as mentioned, UMTRI[146] found AEB systems produced an estimated 46 percent reduction in applicable rear-end crashes when combined with forward collision alerts, which alone showed only 21 percent reduction[147].

A recent IIHS study[148] of 2009-2016 crash data from 23 States suggested increasing AEB technology effectiveness in certain crash situations is changing the rear-end crash problem. The Institute’s analysis provided insight into current AEB system performance and future improvement opportunities. The study identified rear-end crash types where striking vehicles with AEB were over-represented compared to those without AEB[149]. For instance, IIHS found striking vehicles in the following rear-end crashes were more likely to have AEB: (1) striking vehicles turning versus moving straight; (2) struck vehicles turning or changing lanes versus slowing or stopped; (3) struck vehicles not passenger vehicles or special use vehicles versus passenger cars; (4) crashes on snowy or icy roads; or (5) crashes on roads with 112.7 kph (70 mph) speed limits versus 64.4 to 72.4 kph (40 to 45 mph) limits. Overall, the study found 25.3 percent of crashes where striking vehicles had AEB had at least one of these over-represented characteristics, compared to 15.9 percent of impacts by non-AEB-equipped vehicles.

These results suggest tests used to evaluate AEB system performance by NCAP and other consumer information programs are influencing countermeasure development to minimize targeted crash problems. However, results also imply AEB systems haven’t fully realized their crash reduction potential. While effective at addressing common rear-end crashes, they are less effective at atypical crashes. IIHS found that in 2016, nearly 300,000 (15 percent) of police-reported two-vehicle rear-end crashes involved one of the rear-end crashes mentioned above. The Institute suggested vehicle manufacturers would be encouraged to improve AEB system designs for situations where AEB was over-represented if consumer programs incorporated tests replicating these rear-end crash events, such as angled target vehicles simulating struck vehicles changing lanes. IIHS cautioned (and NHTSA agrees) that new testing protocols should not degrade performance in typical crash situations, create unintended safety consequences, or adversely affect AEB use due to nuisance activations.

While recent studies suggest AEB systems (CIB and DBS) have collectively reduced rear-impact crashes, it’s unclear how effective each system is standalone, and whether individual effectiveness changes for certain crash scenarios, environmental conditions, or driver factors (poor judgment, distraction). Furthermore, the Agency is unaware of current-generation AEB system studies determining CIB and DBS individual crash reduction contributions.

Before adopting AEB into NCAP, NHTSA reviewed 2003-2009 National Automotive Sampling System Crashworthiness Data System (NASS CDS) data to define rear-end crash target populations[150]. At the time of analysis, the Agency concluded CIB and DBS target crash populations were mutually exclusive, including crashes where drivers either did not brake (CIB) or braked (DBS). Crash data analysis showed drivers braked in ~half of crashes and did not brake in the other half. However, Volpe’s 2011-2015 FARS and GES data analysis showed more conservative brake rates, finding drivers braked in just 8 percent of fatal rear-end crashes and 20 percent of injury crashes. The study also showed drivers made no crash avoidance attempts (no braking, steering, accelerating) for 56 percent of fatal crashes and 21 percent of injury crashes[151]. Brake rate differences in studies may be due to target crash population refinements for NHTSA’s original analysis and crash database data collection method differences. For instance, high-speed crashes were excluded from NHTSA’s target crash population review because AEB systems tested at the time had limited speed reduction capabilities.

From the refined target crash population, NHTSA computed preliminary safety benefits for both CIB and DBS from a limited number of CIB and DBS-equipped vehicles tested using early versions of Agency test procedures based on speed reduction capabilities[152]. The Agency recognized CIB and DBS systems at the time had limited capabilities and could not address serious crashes with likely fatalities. Nevertheless, the Agency tentatively found if CIB systems alone were equipped on all light vehicles, they could potentially prevent ~40,000 minor/moderate injuries (AIS 1-2), 640 serious-to-critical injuries (AIS 3-5), and save ~40 annual lives. If DBS systems alone were equipped on all light vehicles, they could potentially prevent ~107,000 minor/moderate injuries (AIS 1-2), 2,100 serious-to-critical injuries (AIS 3-5), and save ~25 annual lives. These CIB and DBS safety benefits were considered incremental to FCW alert benefits[153].

NHTSA’s analysis showed merit in testing vehicle performance in situations where drivers either do not brake (CIB) or brake (DBS). Volpe’s recent braking behavior/rate analysis further validates the need to assess CIB and DBS separately. Considering this and the fact NHTSA cannot currently differentiate CIB and DBS system individual effectiveness, NHTSA tentatively believes NCAP should continue assessing CIB and DBS system performance individually. However, the Agency acknowledges that, believing AEB systems have advanced significantly, it is appropriate to consider revising NCAP performance envelopes and dynamic scenarios to acknowledge and encourage such advances.

The following sections detail CIB and DBS systems, specifically NCAP’s current test procedures and potential updated test programs for modern AEB systems. The Agency seeks comment on how NCAP can encourage maximum AEB safety benefits and potentially reduce test numbers. Comments are also sought on future AEB suggestions beyond near-term upgrades.

a. Dynamic Brake Support (DBS)

In response to FCW alerts or drivers noticing imminent crash scenarios, drivers may brake to avoid rear-end crashes. In cases where driver braking is insufficient to prevent collisions, DBS can automatically supplement driver braking to prevent or mitigate crashes. Similar to FCW and CIB systems, DBS systems use forward-looking sensors (radar, lidar, and/or vision-based) to detect vehicles ahead and monitor vehicle operating conditions like speed or braking. However, DBS systems actively supplement braking to assist drivers, whereas FCW systems only warn drivers of potential crash threats, and CIB systems activate when rear-end crashes are imminent, but drivers haven’t manually braked[154].

NCAP’s current DBS test procedure[155] includes the same three rear-end crash scenarios as the FCW system performance test procedure—LVS, LVD, and LVM—but most test speed combinations differ (the single exception being shared LVM tests with SV and POV speeds of 72.4 and 32.2 kph (45 and 20 mph)). In addition, DBS performance assessment includes a Steel Trench Plate (STP) false positive suppression test, conducted at two test speeds. This fourth scenario evaluates BSI system propensity for inappropriate activation in non-critical driving scenarios posing no safety risk to vehicle occupants. For the first three scenarios, where braking is expected, SVs must provide sufficient supplemental braking to avoid POV contact to pass trials. In the DBS false positive test scenario, performance criteria are minimal to no activation at both test speeds[156].

As in FCW system performance tests, the vehicle subjected to DBS test scenarios is the SV. The FCW test procedure (using professional drivers for acceleration, braking, and steering during tests) stipulates a mid-size passenger car as the POV. The DBS test procedure (relying solely on programmable brake controllers and vehicle DBS systems for braking), however, uses a surrogate (target vehicle) to limit potential damage to SVs and/or test equipment in collisions.

The target vehicle currently used as the POV by NCAP for DBS testing is the Subject Surrogate Vehicle, or SSV. The SSV, developed by NHTSA for track testing, appears as a “real” vehicle to camera, radar, and lidar sensors used by AEB systems. The SSV system comprises (a) a shell[157], a visually and dimensionally accurate passenger car representation; (b) a slider and load frame assembly to which the shell is attached; (c) a two-rail track for slider operation; (d) a road-based lateral restraint track; and (e) a tow vehicle pulling the SSV and peripherals down the test track during trials where POVs (SSVs) must be in motion. A brief discussion on GVT use, discussed earlier in the BSI section, as an alternative to SSV for future DBS and CIB testing is included later[158].

A short description of each DBS system performance test scenario, and passing result requirements, follows:

Lead Vehicle Stopped (LVS)—The SV encounters a stopped POV on a straight road. The SV moves at 40.2 kph (25 mph), and the POV is stationary. The SV throttle is released within 500 ms after the SV issues an FCW alert, and the SV brake is applied at a TTC of 1.1 s (nominal 12.2 m (40 ft.) headway). To pass, the SV must not contact the POV.
Lead Vehicle Decelerating (LVD)—The SV encounters a POV slowing with constant deceleration ahead on a straight road. The SV and POV both travel at 56.3 kph (35 mph) with 13.8 m (45.3 ft.) initial headway. The POV brakes at a constant 0.3g deceleration in front of the SV, after which SV throttle is released within 500 ms after FCW alert, and SV brakes are applied at a TTC of 1.4 s (nominal 9.6 m (31.5 ft.) headway). To pass, the SV must not contact the POV.
Lead Vehicle Moving (LVM)—The SV encounters a slower-moving POV directly ahead on a straight road. In the first test, the SV and POV travel on a straight road at constant speeds of 40.2 kph (25 mph) and 16.1 kph (10 mph), respectively. In the second test, the SV and POV travel at constant speeds of 72.4 kph (45 mph) and 32.2 kph (20 mph), respectively. In both tests, the SV throttle is released within 500 ms after FCW alerts, and SV brakes are applied at a TTC of 1 s (nominal 6.7 m (22 ft.) headway in the first test, and 11.3 m (37 ft.) in the second). To pass these tests, the SV must not contact the POV.
Steel Trench Plate (STP) test (false positive suppression)—The SV is driven over a 2.4 m x 3.7 m x 25.4 mm (8 ft. x 12 ft. x 1 in.) steel trench plate at 40.2 kph (25 mph) and 72.4 kph (45 mph). If no FCW alert is issued by a TTC of 2.1 s, the SV throttle is released within 500 ms of a TTC of 2.1 s, and SV brakes are applied at a TTC of 1.1 s (nominal 12.3 m (40 ft.) distance from STP edge at 40.2 kph (25 mph), or 22.3 m (73 ft.) at 72.4 kph (45 mph)). To pass, the performance criterion is non-activation, as defined above.

To pass NCAP’s DBS system performance criteria, SVs must currently pass five of seven trials for each of the six test conditions.

As previously mentioned, NCAP’s LVS, LVM, and LVD test scenarios for DBS evaluations are similar to FCW assessments, thus corresponding well with real-world crash data and having similar target crash populations. NHTSA’s 2011-2015 rear-end crash data analysis from FARS and GES showed target crash populations of 65 percent for the LVS scenario, 22 percent for LVD, and 10 percent for LVM[159]. Furthermore, Volpe’s independent 2011-2015 data set review showed for rear-end crashes on roads with posted speeds of 40.2 kph (25 mph) or less, 56.3 kph (35 mph) or less, and 72.4 kph (45 mph) or less, fatality rates were 2 percent, 11 percent, and 28 percent, respectively. MAIS 1-5 injuries were observed in 6 percent of rear-end crashes on roads with posted speeds of 40.2 kph (25 mph) or less, 30 percent with 56.3 kph (35 mph) or less, and 63 percent with 72.4 kph (45 mph) or less.

b. Crash Imminent Braking (CIB)

If drivers take no braking action when rear-end crashes are imminent, CIB systems use the same forward-looking sensors as DBS systems to automatically brake, slowing or stopping vehicles. Braking amounts vary by manufacturer, with several systems designed to achieve maximum vehicle deceleration just before impact. Reviewing 2017-2019 NCAP CIB test data, NHTSA observed a 0.31-1.27g deceleration range during trials providing speed reductions meeting CIB performance criteria for given test conditions. Unlike DBS systems supplementing driver braking, CIB systems activate when drivers haven’t applied brake pedals[154].

Consumer Reports’ 2019 subscriber survey found 81 percent of vehicle owners satisfied with AEB technology, 54 percent said it helped avoid crashes, and 61 percent trusted the system to work every time[144]. Furthermore, IIHS’s 2017 study found rear-end collisions decreased 50 percent for vehicles with AEB and FCW[145]. Similarly, as mentioned, UMTRI[146] found AEB systems produced an estimated 46 percent reduction in applicable rear-end crashes when combined with forward collision alerts, which alone showed only a 21 percent reduction[147].

NCAP’s current CIB test procedure[160] includes the same four test scenarios (LVS, LVD, LVM, and STP false positive suppression test) and speeds as DBS tests, but performance criteria vary slightly. The LVM 40.2 kph/16.1 kph (25 mph/10 mph) test condition stipulates SVs must not contact POVs. LVS, LVD, and LVM 72.4 kph/32.2 kph (45 mph/20 mph) test conditions permit SV-to-POV contact but require minimum SV speed reductions. In CIB false positive tests, performance criteria are minimal to no activation. Similar to NCAP’s DBS tests, the SSV is the POV currently used in CIB testing. A short description of each test scenario and passing result requirements follows:

LVS—SVs encounter stopped POVs on straight roads. SVs move at 40.2 kph (25 mph), and POVs (SSVs) are stationary. SV throttles are released within 500 ms after FCW alerts. To pass, SV speed reduction from CIB intervention must be ≥15.8 kph (9.8 mph).
LVD—SVs encounter POVs slowing with constant deceleration ahead on straight roads. SVs and POVs both travel at 56.3 kph (35 mph) with 13.8 m (45.3 ft.) initial headway. POVs then decelerate, braking at a constant 0.3g deceleration ahead of SVs, after which SV throttles are released within 500 ms after FCW alerts. To pass, SV speed reduction from CIB intervention must be ≥16.9 kph (10.5 mph).
LVM—SVs encounter slower-moving POVs directly ahead on straight roads. In the first test, SVs and POVs travel on straight roads at constant speeds of 40.2 kph (25 mph) and 16.1 kph (10 mph), respectively. In the second test, SVs and POVs travel at constant speeds of 72.4 kph (45 mph) and 32.2 kph (20 mph), respectively. In both tests, SV throttles are released within 500 ms after FCW alerts. To pass the first test, SVs must not contact POVs. To pass the second, SV speed reduction from CIB intervention must be ≥15.8 kph (9.8 mph).
STP test (false positive suppression)—SVs are driven towards steel trench plates at 40.2 kph (25 mph) in one test and 72.4 kph (45 mph) in the other. If FCW alerts are issued, SV throttles are released within 500 ms of alerts. If no FCW alerts, throttles are not released until test validity periods (when all test specifications and tolerances must be met) have passed. To pass, SVs must not achieve peak deceleration ≥0.5g during STP approach.

To pass NCAP’s CIB system performance criteria, SVs must pass five of seven trials for each of the six test conditions.

Similar to FCW and DBS, NCAP’s CIB test scenarios correlate to dynamically distinct rear-end crash data discussed earlier. The Agency’s 2011-2015 crash data analysis showed LVS, LVD, and LVM scenarios represented 65 percent, 22 percent, and 10 percent, respectively, of all rear-end crashes[161]. Volpe’s 2011-2015 data set independent review showed for rear-end crashes on roads with posted speeds ≤40.2 kph (25 mph), 56.3 kph (35 mph), and 72.4 kph (45 mph), fatality rates were 2 percent, 11 percent, and 28 percent, respectively. Also, MAIS 1-5 injuries were observed in 6 percent of rear-end crashes on roads with posted speeds ≤40.2 kph (25 mph), 30 percent with ≤56.3 kph (35 mph), and 63 percent with ≤72.4 kph (45 mph).

c. Current State of AEB Technology

When NHTSA’s CIB test scenarios were developed, few vehicles had this technology, and those equipped had limited capabilities. Since then, CIB system fitment rates have significantly increased, partly due to a March 2016 industry voluntary commitment. At that time, 20 vehicle manufacturers, representing over 99 percent of U.S. light motor vehicle sales, voluntarily committed to install AEB systems on light motor vehicles[162]. Per this commitment, manufacturers would make FCW and CIB standard on virtually all light-duty vehicles with ≤3,855.5 kg (8,500 pounds) gross vehicle weight rating (GVWR) by September 1, 2022, and all trucks with 3,856.0 to 4,535.9 kg (8,501 to 10,000 pounds) GVWR by September 1, 2025. Conforming vehicles must have (1) AEB systems earning at least an “advanced” IIHS rating in front crash prevention track tests and (2) FCW systems meeting two of NCAP’s three FCW test scenario performance requirements[163]. Manufacturers pledged to submit annual progress reports, published by IIHS and NHTSA. In 2017, the first reporting year, ~30 percent of the fleet was CIB-equipped (though many systems were not designed to meet voluntary commitment thresholds), while participating manufacturers equipped 75 percent of their fleet in 2019[164].

While the voluntary commitment increased fitment rates, the agreement’s AEB system stringency is lower than NCAP’s. The voluntary commitment included front crash prevention track tests less stringent than NCAP performance thresholds, and fewer in number. The Agency was aware of these differences but considered the voluntary commitment a path to greater fleet penetration[165].

As fitment increased, CIB system sensor technology also advanced significantly. In 2017, many systems were not designed to meet voluntary commitment thresholds, while in 2019, most vehicles with FCW and CIB systems could pass all relevant NCAP test scenarios. NHTSA notes NCAP’s CIB test requirements currently require ≥15.8 kph (9.8 mph) speed reduction in the program’s LVS test, more stringent than the voluntary commitment allowing 8.0 kph (5 mph) speed reduction in IIHS 19.3 or 40.2 kph (12 or 25 mph) LVS tests[166]. For model year 2021, pass rates (manufacturer-reported) for NCAP’s FCW and CIB tests for vehicles[167] with these technologies and manufacturer-submitted data were 88.8 percent and 69.5 percent, respectively[168]. Furthermore, NHTSA found 63 percent of model year 2017 vehicles did not contact POVs in LVS scenarios during Agency testing, while 100 percent of model year 2021 vehicles did not contact POVs when tested[169]. As such, the Agency believes current CIB system performance far exceeds NCAP’s current testing requirements, making it feasible to update the program’s CIB test conditions to further safety improvements. Recent NHTSA research supports this assertion.

d. NHTSA’s CIB Characterization Study

Similar to fleet testing for PAEB, the Agency conducted CIB characterization tests using a sample of MY 2020 NCAP test vehicles from various manufacturers. The goal was to quantify current CIB system performance using LVS and LVD test scenarios, but with expanded input conditions. Testing was per the CIB test procedure above; however, several scenarios were repeated to assess how procedural changes (test speed and deceleration magnitude increases) affected CIB performance.

For additional LVD tests, the Agency evaluated how changes to vehicle speed (72.4 kph vs. 56.3 kph (45 mph vs. 35 mph)) or deceleration magnitude (0.5g vs. 0.3g) affected CIB performance, as shown in Table 3.

Details of NHTSA’s CIB characterization study are below (speeds in kph (mph)):

Table 2—Nominal LVS Matrix
| SV speed, (kph/mph) | POV speed, (kph/mph) |
|—|—|
| 40.2/25 | 0/0 |
| 48.3/30 | 0/0 |
| 56.3/35 | 0/0 |
| 64.4/40 | 0/0 |
| 72.4/45 | 0/0 |

Table 3—Nominal LVD Matrix
| SV speed, (kph/mph) | POV speed, (kph/mph) | Peak deceleration (g) | Minimum distance, (mft.) |
|—|—|—|—|
| 56.3/35 | 56.3/35 | 0.3 | 13.8/45.3 |
| 56.3/35 | 56.3/35 | 0.5 | 13.8/45.3 |
| 72.4/45 | 72.4/45 | 0.3 | 13.8/45.3 |

No additional LVM or STP false positive assessments were done in the CIB characterization study for several reasons. First, NHTSA’s 2011-2015 FARS and GES rear-end data review showed LVS and LVD rear-end scenarios had the highest crash and MAIS 1-5 injury numbers. Table A-1 shows 1,099,868 LVS, 374,624 LVD, and 174,217 LVM annual crashes[171]. Also, there were 561,842 MAIS 1-5 injuries from LVS crashes, 196,731 for LVD, and 97,402 for LVM. LVS also had the second-highest fatalities. Secondly, it was unclear if additional STP false positive tests would provide useful data. When STP tests were initially developed, many AEB systems relied solely on radar for lead vehicle detection. Today, most vehicles use camera-only or fused systems (camera and radar). While the Agency has observed false positive test failures during CIB and DBS NCAP evaluations with radar-only systems, none have been observed with camera-only or fused systems. While some radar-only systems struggled classifying STPs, camera-only and fused systems have not exhibited this issue[172]. Therefore, the Agency believes STP false positive assessments removal from NCAP’s AEB evaluation matrix in this NCAP update may be appropriate and requests comment.

The Agency increased test scenario speeds in its CIB characterization study because Volpe’s independent 2011-2015 FARS data set analysis found speeding a factor in 42 percent of fatal rear-end crashes[173]. Volpe’s analysis also showed ~28 percent of fatalities and 63 percent of injuries in rear-end crashes occurred on roads with posted speeds ≤72.4 kph (45 mph). When travel speed was reported in FARS and GES, ~7 percent of fatal and 34 percent of police-reported rear-end injury crashes occurred at speeds ≤72.4 kph (45 mph)[174]. This data suggested merit in assessing newer vehicle capabilities using LVS tests at higher speeds, gauging current-generation CIB system ability to address more rear-end crashes, especially those causing the most serious and fatal injuries. The Agency also reasoned increasing test speed in NCAP’s LVS scenario, in particular, was most appropriate, as this scenario could require the greatest speed reduction authority for safety benefit realization. Historically, it has also been a challenging scenario for forward-looking sensing systems, particularly at high speeds.

While NHTSA acknowledges most fatal rear-end crashes (72 percent) occurred on roads with >72.4 kph (45 mph) posted speeds, these higher speeds were not assessed in Agency characterization testing. Before testing, the Agency had safety concerns conducting LVS tests at ≥80.5 kph (50 mph) due to test track length limitations, laboratory personnel safety, and potential SV or test equipment damage. However, as discussed next, data collected during Agency testing showed higher test speeds may be feasible, as several vehicles provided complete crash avoidance at 72.4 kph (45 mph).

NHTSA’s modified LVD scenario evaluation aimed to document current CIB system performance in more demanding LVD-based driving situations. The Agency also planned to use test results to determine the feasibility of increasing NCAP’s LVD test stringency. Compared to LVD test conditions in NHTSA’s current CIB test procedure, modified LVD tests, as shown in Table 3, either (1) maintained existing 13.8 m (45.3 ft.) SV-to-POV headway and 0.3g POV deceleration profile, but increased POV and SV travel speed from 56.3 to 72.4 kph (35 to 45 mph), or (2) maintained existing 13.8 m (45.3 ft.) SV-to-POV headway and 56.3 kph (35 mph) POV and SV speeds, but increased average POV deceleration magnitude to 0.5g.

NHTSA’s interest in the first LVD procedural change aligned with LVS scenario changes—significant fatalities and injuries in rear-end crashes occurred at higher speeds. The second change addressed situations where lead vehicle drivers brake aggressively, giving following vehicle drivers even less time to avoid or mitigate crashes than with 0.3g lead vehicle braking. The Agency reasoned these LVD scenario changes would introduce more stringent scenarios than in NHTSA’s current CIB test procedure, helping the Agency comprehensively understand current CIB system capabilities.

Test reports related to NHTSA’s CIB characterization testing are available in the docket for this notice.

e. Updates to NCAP’s CIB Testing

Generally, this study has enabled NHTSA to assess current CIB system performance and evaluate technology future potential for new model year vehicle fleets. The study showed many current fleet vehicles could repeatedly achieve complete crash avoidance at higher test speeds, shorter SV-to-POV headways, and generally more aggressive conditions than specified in the Agency’s current NCAP CIB test procedure. This study also provided the Agency with new ways to consider differentiating CIB system performance for future NCAP ratings purposes. Furthermore, it provided underlying support for NCAP to propose adjustments to current CIB performance requirements to address real-end crashes causing more real-world injuries and fatalities. Accordingly, the Agency proposes several changes to its CIB test procedure for this NCAP upgrade. These changes are outlined below per test scenario. For the LVS scenario, the Agency proposes:

Increased SV test speeds and assessment methodology similar to that proposed for PAEB system performance. CIB system performance for LVS scenarios will be assessed over a test speed range. The Agency proposes a minimum SV test speed of 40 kph (24.9 mph), similar to the 2019 PAEB test procedure—40.2 kph (25 mph), and a maximum SV test speed of 80.0 kph (49.7 mph). The Agency proposes increasing SV test speed in 10 kph (6.2 mph) increments from minimum to maximum test speed for LVS assessment.

Agency characterization testing showed raising SV speed in NCAP’s LVS test to encourage improved CIB system performance is feasible. Several vehicles repeatedly achieved full crash avoidance (no contact) at speeds up to 72.4 kph (45 mph) for LVS test scenarios. Furthermore, NHTSA recognizes Euro NCAP performs its Car-to-Car Rear stationary (CCRs) scenario, comparable to Agency LVS tests, at speeds up to 80 kph (49.7 mph) for systems with AEB, suggesting higher test speeds are practicable[175]. Thus, NHTSA believes harmonizing with Euro NCAP on the 80 kph (49.7 mph) maximum LVS test speed is appropriate, better addressing higher severity, high-speed crash problems and reducing fatalities and serious injuries. While Euro NCAP’s protocol specifies a 10 kph (6.2 mph) minimum SV test speed for CCRs scenarios for AEB systems also offering FCW, the Agency sees no reason to perform its LVS test at a speed less than its existing test procedure (40.2 kph (25 mph)). Therefore, it is not proposed to harmonize with Euro NCAP regarding minimum test speed.

Revised performance requirement. Instead of speed reduction, as currently specified in NHTSA’s CIB test procedure for LVS scenarios, SVs must avoid POV target contact to pass trials. Similar to PAEB, this should limit pedestrian mannequin and SV damage during testing and reduce questioned or invalidated results.
Changes to the number of test trials for LVS scenarios. Currently, NHTSA’s CIB test procedure requires vehicles meet performance criteria (specified speed reduction) for five of seven trials. However, similar to the PAEB assessment proposal, the Agency proposes only one test trial be conducted per test speed assessed (40, 50, 60, 70, and 80 kph or 24.9, 31.1, 37.3, 43.5, and 49.7 mph) if SVs do not contact POV targets during the first valid trial for each speed. For a given test condition, testing starts at the 40 kph (24.9 mph) minimum speed. To pass, tests must be valid (specifications and tolerances met), and SVs must not contact POVs. If SVs do not contact POVs during valid first tests, test speed incrementally increases by 10 kph (6.2 mph), and the next test in sequence is performed. Unless SVs contact POVs, iteration continues to maximum 80 kph (31.1 mph) test speed evaluation. If SVs contact POVs, and relative longitudinal velocity between SVs and POVs is ≤50 percent of initial SV speed, the Agency will perform four additional (repeated) tests at the same speed where impact occurred. Vehicles must not contact POVs for at least three of five tests at that speed to pass that specific test condition and test speed combination[176]. If SVs contact POVs during valid test conditions (whether first test at a speed or a subsequent trial at that speed), and relative impact velocity exceeds 50 percent of initial SV speed, no additional tests will be conducted at that speed and condition, and SVs are considered to have failed the test condition at that speed.

The Agency is pursuing an assessment approach for LVS CIB scenarios similar to PAEB systems to reduce test burden, given additional proposed test speeds. NHTSA believes this alternative approach will continue ensuring passing CIB systems represent robust designs offering enhanced performance and safety.

For LVD scenarios, the Agency proposes:

The Agency also requests comment on whether to incorporate additional SV test speeds for LVD test scenarios, specifically 60, 70, and 80 kph (37.3, 43.5, and 49.7 mph), or if testing at only 50 kph (31.1 mph) and 80 kph (49.7 mph) would suffice. As mentioned earlier, Volpe’s 2011-2015 FARS data set analysis showed most crashes occurred on roads with posted speeds >72.4 kph (45 mph), suggesting higher speed testing may be warranted for all CIB test scenarios. The Agency has not yet performed testing at 80 kph (49.7 mph) due to safety concerns with laboratory abilities to safely execute such tests and limited test track space, as this scenario requires both SVs and POVs to travel at the same speed at test validity period onset. However, NHTSA believes (1) given characterization study results, especially braking performance in LVS tests, (2) tested vehicles may have higher POV classification confidence for LVD tests than LVS tests, as POVs are always moving in LVD tests, and (3) POVs will be GVTs, using robotic platforms for movement, rather than SSVs towed on test track monorails, vehicles in current fleets will likely also perform well in higher speed LVD tests. To validate this, NHTSA will research vehicle performance at 50 kph (31.1 mph) to 80 kph (49.7 mph) speeds for 12 and 40 m (39.4 and 131.2 ft.) headways and POV deceleration magnitudes of 0.4 and 0.5 g for LVD CIB test scenarios next year. Pending research outcomes, the Agency may consider adopting additional higher test speeds (60, 70, and/or 80 kph (37.3, 43.5, and/or 49.7 mph)) for LVD test scenarios in NCAP. The Agency requests comment on appropriate SV-to-POV headway and deceleration magnitude(s) if any or all of these additional test speeds are adopted. If additional test speeds are adopted, the Agency would implement an assessment methodology similar to that proposed for CIB LVS scenarios, increasing SV test speed in 10 kph (6.2 mph) increments from minimum to maximum test speed for LVD assessment.

Reduced SV-to-POV headway. NCAP’s CIB test procedure currently specifies 13.8 m (45.3 ft.) SV-to-POV headway for LVD scenarios. The Agency proposes reducing the prescribed headway to 12 m (39.4 ft.) to harmonize with Euro NCAP’s CCRb scenario. Given the proposed test speed reduction, the Agency believes headway reduction is appropriate to maintain similar stringency with its current LVD test condition. While Euro NCAP also specifies an additional 40 m (131.2 ft.) SV-to-POV headway, the Agency is not proposing this additional assessment in this proposal. NHTSA does not believe adopting 40 m (131.2 ft.) as an additional, less stringent headway would provide safety benefits, unnecessarily increasing test burden.
Increased deceleration magnitude. The Agency proposes increasing POV deceleration magnitude currently specified in its CIB test procedure for LVD scenarios from 0.3 g to 0.5 g. In the Agency’s CIB characterization study, some vehicles repeatedly achieved full crash avoidance (no contact) for all trials when POVs executed 0.5 g braking maneuvers in LVD conditions with 35 mph SV test speeds and 13.8 m (45.3 ft.) SV-to-POV headway. Although the test speed used in the Agency’s study was slightly lower than proposed for LVD tests and SV-to-POV headway was slightly longer, NHTSA believes adopting a higher POV deceleration magnitude for future LVD testing is reasonable. The Agency notes a 0.5 g deceleration falls within the range of deceleration magnitudes specified by Euro NCAP in its AEB Car-to-Car systems test protocol, Version 3.0.3, dated April 2021, for CCRb scenarios. In its CCRb test, Euro NCAP specifies POV deceleration magnitudes of 2 m/s² and 6 m/s² (approximately 0.2 to 0.6 g) for 12 m (39.4 ft.) SV-to-POV headway and 50 kph (31.1 mph) SV test speed[177]. As the Agency has proposed this reduced headway and test speed for its LVD testing, it reasons adopting a 0.5 g POV deceleration magnitude is also practicable. The Agency is not proposing 0.6 g as the POV deceleration magnitude in LVD tests because it has observed tire flat spots developing on POV targets during research testing with the Guided Soft Target (GST) system[178] to assess Traffic Jam Assist (TJA) systems. TJA testing required a lead vehicle deceleration maneuver, accelerates, then decelerates (LVDAD) scenario similar to the Agency’s CIB LVD test[179]. During this testing, NHTSA also found it more difficult to accurately control deceleration above 0.5 g braking maneuvers[180]. Extensive tuning efforts related to GST brake applications to rectify issues were unsuccessful in consistently meeting 0.6 g POV deceleration test tolerances for LVDAD tests, and a recommendation was made to reduce maximum nominal POV deceleration from 0.6 g to 0.5 g for future testing. In its report findings, the Agency also noted 0.6 g deceleration is very close to GST’s robotic platform maximum braking capability and to the default magnitude used by LPRVs during emergency stops (maximum deceleration). Thus, the Agency concluded a maximum POV deceleration decrease should also reduce equipment wear, particularly for system tires and braking components, improving test efficiency. However, the Agency acknowledges newer robotic platforms with greater capabilities are now available, potentially resolving issues observed in Agency TJA testing. As such, the Agency requests comment on whether adopting a 0.6 g POV deceleration magnitude instead of the proposed 0.5 g is feasible.
Alternative performance criterion. Instead of speed reduction, as currently specified in NHTSA’s CIB test procedure for LVD scenarios, vehicles must avoid POV target contact to pass trials.
Changes to the number of test trials required for LVD scenarios. NHTSA is adopting a test trial conduct approach identical to that described for CIB LVS scenarios, regardless of adopted test speeds (one speed, 50 kph (31.1 mph); two speeds, 50 kph (31.1 mph) and 80 kph (49.7 mph); or four speeds, 50, 60, 70, and 80 kph (31.1, 37.3, 43.5, and 49.7 mph)). If only one or two test speeds are selected for inclusion, the Agency seeks comment on whether alternatively requiring 7 trials per test speed, and requiring 5 of 7 trials to pass the “no contact” performance criterion, is more appropriate.

For LVM scenarios, the Agency proposes:

Increased SV test speeds. NHTSA proposes assessing CIB system performance for LVM scenarios over a test speed range, similar to the LVS scenario. The Agency proposes a minimum SV test speed of 40 kph (24.9 mph), nearly equivalent to the 40.2 kph (25 mph) test speed in NHTSA’s current CIB test procedure, and a maximum SV test speed of 80 kph (49.7 mph), slightly higher than the 72.4 kph (45 mph) specified for the second LVM test condition in NHTSA’s current CIB test procedure. The Agency proposes increasing SV test speed in 10 kph (6.2 mph) increments from minimum to maximum test speed for LVM assessment.

The Agency did not conduct additional LVM testing in its CIB characterization study. Nonetheless, NHTSA believes raising SV speed in NCAP’s LVM test to encourage improved CIB system performance is feasible, as current NCAP CIB LVM tests (SV speed 72.4 kph (45 mph) and POV speed 32.2 kph (20 mph)) have shown many vehicles can stop without POV target contact for each required trial. Furthermore, NHTSA recognizes Euro NCAP performs its Car-to-Car Rear moving (CCRm) scenario, comparable to Agency LVM tests, at speeds up to 80 kph (49.7 mph), suggesting higher SV test speeds are also practicable[181]. Thus, NHTSA believes harmonizing with Euro NCAP on the 80 kph (49.7 mph) maximum SV test speed in the Agency’s LVM test is appropriate, also addressing high-speed crashes and further reducing fatalities and serious injuries. While Euro NCAP’s protocol prescribes a 30 kph (18.6 mph) minimum SV test speed for CCRm scenarios for vehicles with AEB systems[182], the Agency sees no reason to perform its LVM test at a speed lower than its existing test procedure (40.2 kph (25 mph)). Therefore, it is not proposed to harmonize with Euro NCAP regarding minimum test speed.

Alternative POV test speed for all test conditions. While the Agency’s CIB test procedure currently specifies a 16.1 kph (10 mph) POV test speed with 40.2 kph (25 mph) SV speed and 32.2 kph (20 mph) POV test speed with 72.4 kph (45 mph) SV speed, the Agency proposes using a 20 kph (12.4 mph) POV test speed for every SV test speed assessed for LVM scenarios: 40 to 80 kph (24.9 to 49.7 mph), increased in 10.0 kph (6.2 mph) increments. NHTSA recognizes Euro NCAP’s CCRm protocol specifies a 20 kph (12.4 mph) POV test speed, stipulated for similar testing by various other vehicle safety ratings programs. With this proposed NCAP upgrade, NHTSA sees no reason to deviate from other testing organizations regarding POV speed for its LVM test.
Performance criterion of “no contact.” Instead of speed reduction, as currently specified in NHTSA’s CIB test procedure for the Agency’s higher speed LVM scenario (72.4 kph (45 mph) POV and 32.2 kph (20 mph) POV speed), SVs must avoid POV target contact to pass trials for each test speed assessed for LVM scenarios: 40 to 80 kph (24.9 to 49.7 mph), increased in 10 kph (6.2 mph) increments.
Changes to the number of test trials required for LVM scenarios. NHTSA is adopting a test trial conduct approach identical to that described for CIB LVS scenarios. For proposed CIB LVM tests, the Agency would require one trial per SV speed increment and four repeat trials in case of test failures where SVs have relative impact velocity ≤50 percent of initial speed.

NHTSA has chosen to harmonize with Euro NCAP in many respects as it recognizes the rear-end crash problem, as defined by the most frequent and dynamically distinct pre-crash scenarios, could be changing as AEB-equipped vehicles become more prevalent in the fleet.