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Proposed Safety Standards for Automatic Emergency Braking Systems

July 13, 2023
The NHTSA is proposing a new Federal Motor Vehicle Safety Standard to require automatic emergency braking systems including pedestrian AEB on light vehicles.

What you'll learn:

  • What are the specifics of an AEB system, and the statistics behind its push for implementation.
  • Requirements in the NHTSA's proposed AEB standard that must be met.
  • Best practices for submitting comments on the proposal.

The regulations game is heating up and not just with onset of warmer weather. The National Highway Traffic Safety Administration (NHTSA) is proposing a new Federal Motor Vehicle Safety Standard (Docket No. NHTSA-2023-0021) to require automatic emergency braking (AEB) systems, including pedestrian AEB, on light vehicles.

An AEB system uses various sensor technologies and subsystems that work together to detect when the vehicle is in a crash-imminent situation. It automatically applies the vehicle brakes if the driver hasn’t done so, or it applies more braking force to supplement the driver's braking as necessary to avoid or mitigate the severity of the crash.

Mandating AEB systems would address a clear and, in the case of pedestrian deaths, growing safety problem. In 2019, there were 6,272 pedestrian fatalities in motor vehicle crashes, representing 17% of all motor vehicle fatalities. The agency’s analysis of the safety problem focuses on the calendar year 2019 because it’s the most recent year without the prominent effect of the COVID-19 pandemic.

PAEB systems function like lead vehicle AEB systems but detect pedestrians in front of the vehicle. PAEB systems intervene in crash imminent situations in which the pedestrian is either directly in the path of a vehicle or entering the path of the vehicle. There were 38,824 fatalities in motor vehicle crashes on U.S. roadways in 2020 and early estimates put the number of fatalities at 42,915 for 2021. This is the highest number since 2005.       

Saving Lives

The NHTSA projects that this proposed rule, if finalized, would save at least 360 lives a year and reduce injuries by at least 24,000 annually. Said U.S. Transportation Secretary Pete Buttigieg, “Just as lifesaving innovations from previous generations like seat belts and air bags have helped improve safety, requiring automatic emergency braking on cars and trucks would keep all of us safer on our roads.”  

Added NHTSA Chief Counsel Ann Carlson, “Our proposed rule would require all cars to be able to stop and avoid contact with a vehicle in front of them up to 62 miles per hour. And the proposal would require pedestrian AEB, including requiring that AEB recognize and avoid pedestrians at night.”  

Specifically, the NHTSA indicated that this rule would reduce fatalities by 362 (124 rear-end and 238 pedestrian) annually and reduce injuries by 24,321 (21,649 rear-end and 2,672 pedestrian) annually. In addition, lead vehicle AEB systems would likely yield substantial benefits over the lifetime of the vehicle in property damage avoided.

If adopted as proposed, nearly all U.S. light vehicles (gross vehicle weight rating of 10,000 pounds or less) will be required to have AEB technology three years after the publication of a final rule. 

Comments on the proposed rulemaking must be received on or before 60 days after the date of publication in the Federal Register. Vehicles manufactured on or after September 1, four years after the publication date of a final rule, must meet all requirements. Vehicles manufactured on or after September 1, three years after the publication date of a final rule, must meet all requirements except for the lower-speed PAEB performance test requirements.

AEB Standard Requirements

The proposed standard includes four requirements for AEB systems regarding both lead vehicles and pedestrians.

First, vehicles would be required to have an AEB system that provides the driver with a forward collision warning (FCW) at any forward speed greater than 10 km/h (6.2 mph). NHTSA is proposing that the FCW be presented via auditory and visual modalities when a collision with a lead vehicle or a pedestrian is imminent. Based on NHTSA's research, this proposal includes specifications for the auditory and visual warning components. Additional warning modes, such as haptic, would be allowed.

Second, vehicles would be required to have an AEB system that applies the brakes automatically at any forward speed greater than 10 km/h (6.2 mph) when a collision with a lead vehicle or a pedestrian is imminent. An AEB system active at any speed above 10 km/h (6.2 mph) will be able to mitigate collisions through, at a minimum, speed reduction.

Third, the AEB system would be required to prevent the vehicle from colliding with the lead vehicle or pedestrian test mannequin when tested according to the proposed standard’s test procedures. These test scenarios are designed to ensure that AEB systems are able to perform appropriately in common crash scenarios. In particular, the agency has proposed that pedestrian tests be done in both daylight and darkness.

The final proposed requirement is that a vehicle must detect AEB system malfunctions and notify the driver of any malfunction causing the AEB system not to meet the minimum proposed performance requirements. Malfunctions would include those attributable to sensor obstruction or saturation, such as accumulated snow or debris, dense fog, or sunlight glare. The proposal only includes a specification that the notification be visual.

Making It Happen with Software Upgrades

NHTSA anticipates that systems can achieve the proposed requirements through upgraded software, as all vehicles are assumed to have the necessary hardware. Therefore, the incremental cost associated with this proposed rule reflects the cost of a software upgrade, which will allow current systems to achieve lead vehicle AEB and PAEB functionality that meets the requirements specified in this proposed rule.

The incremental cost per vehicle is estimated at $82.15 for each design-cycle change of the model. When accounting for design cycles and annual sales of new light vehicles, the total annual cost associated with this proposed rule is approximately $282.16 million in 2020 dollars.

The agency also considered specifying a complementary haptic FCW signal as part of the proposed FCW specifications. Currently, only a portion of U.S. vehicles equipped with FCW include a haptic warning component, such as a haptic seat pulse (vibration) or auditory warning based on a driver-selectable setting, a haptic steering-wheel vibration, a brake pulse, or brief deceleration of the vehicle, as part of the FCW.

Malfunction Detection

The NHTSA is proposing that AEB systems must continuously detect system malfunctions. If an AEB system detects a malfunction that prevents it from performing its required safety function, the vehicle would provide the vehicle operator with a warning. The warning would be required to remain active as long as the malfunction exists while the vehicle’s starting system is on.

The agency proposes that the driver must be warned in all instances of component or system failures, sensor obstructions, environmental limitations (like heavy precipitation), or other situations that would prevent a vehicle from meeting the proposed AEB performance requirements.

This proposed rule would not permit manual AEB system disablement at any speed above the specified 10 km/h (6 mph) minimum speed threshold above which the AEB system must operate. The NHTSA seeks comment on whether manual deactivation for an AEB system should be allowed at speeds above 10 km/h (6 mph). It seeks comment on the appropriate performance requirements if the standard were to permit the installation of a manually operated deactivation switch.

Want to Submit Comments?

If you’re interested in preparing and submitting comments, recommendations include:

  • Comments must be written in English.
  • To ensure that your comments are correctly filed in the Docket, please include the Docket Number (NHTSA-2023-0021) in your comments.
  • Your comments must not be more than 15 pages long. NHTSA established this limit to encourage you to write your primary comments in a concise fashion. However, you may attach necessary additional documents to your comments. There’s no limit on the length of the attachments.
  • If you’re submitting comments electronically as a PDF (Adobe) File, NHTSA asks that the documents be submitted using the Optical Character Recognition (OCR) process, thus allowing NHTSA to search and copy certain portions of your submissions. Comments may be submitted to the docket electronically by logging onto the Docket Management System website ( Follow the online instructions for submitting comments.
  • You may also submit two copies of your comments, including the attachments, to Docket Management.
  • If you wish Docket Management to notify you upon its receipt of your comments, enclose a self-addressed, stamped postcard in the envelope containing your comments. Upon receiving your comments, Docket Management will return the postcard by mail.

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