Autonomous emergency braking (AEB), a system first introduced in 2008 by Volvo as Volvo City Safety, has become the unlikely source of a rift between the US regulatory body the National Highway Traffic Safety Administration (NHTSA) and the automakers' representative body in the country, the Alliance for Automotive Innovation (AAI).

From their initial Volvo use case of avoiding low-speed accidents in city driving, AEB systems have evolved significantly. They now utilize a bank of cameras, sensors, radar and lidar to identify potential obstacles, including pedestrians and cyclists, and automatically engage brakes to avoid or mitigate collisions.

Allied with this evolving remit, millions of vehicles in the US are currently under investigation for phantom braking, or the unexpected activation of AEB systems. Toyota, Subaru, Ford, Honda and GM vehicles have all been subject to recalls in the US to fix cases of unexpected activation of AEB systems.

To try and address this issue NHTSA has set stringent requirements for AEB systems (encapsulated in the Federal Motor Vehicle Safety Standard (FMVSS) No. 127 for those with time on their hands) that will come into effect from Sept. 1, 2029.

The problem here is that FMVSS No. 127 is so far out in front of AEB boundaries established in other countries that the AAI considers it unworkable. For example, Europe's regulations for AEB under the General Safety Regulation set speeds between 12.4mph and 37.3mph for AEB operation, while NHTSA wants AEB to be capable at speeds of up to 60mph.

Automakers, in the main, like to be able to act with regulations that are as homogeneous as possible. Regulations that are broadly the same enhance speed to market and reduce development costs. The AAI went even further in June in a letter to NHTSA stating that the AEB mandate is "practically impossible with the current technology". The AAI maintained that although automakers worked with the NHTSA and Insurance Institute for Highway Safety to develop AEB systems, the new standards significantly deviate from the initial agreement on the expected capabilities of the technology (worth recalling here AEB's genesis as Volvo City Safety). The letter highlighted several technical challenges regarding the implementation of the AEB mandate.

According to the AAI, the NHTSA's assumption that existing AEB systems will not significantly contribute to rear-end collisions is flawed given that not all vehicles on the road are equipped with compliant systems. Moreover, the AAI criticized the NHTSA's lack of comprehensive data to substantiate claims that false positives are rare or that the new requirements will not exacerbate the issue.

The AAI recommended that the NHTSA perform a comprehensive risk assessment to quantify the potential rise in rear-end collisions from rule-compliant AEB activations and assess the associated disbenefits, justifying the acceptability of these risks. The AAI stressed that without this evaluation, the regulatory framework may compromise safety rather than enhance it, repeating past experiences with other safety mandates when unintended consequences arose from stringent performance standards.

A closer examination of this spat over one of the more established ADAS (advanced driver assistance systems) technologies is illustrative of the difficulties the industry is facing in moving toward a globally harmonious manifestation of the industry's vision for automated driving. Simply, what's allowable for a Level 4 car in Mainland China, might not be permissible in California or Michigan. What looks like on the surface a localized disagreement over a subset of ADAS technology demonstrates the regulatory difficulties the industry wrestles in the implementation of increasingly complex technologies.

Authored By: Hrishikesh S, Research Analyst, Supply Chain & Technology, S&P Global Mobility

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