In May 2024, the National Highway Traffic Safety Administration (NHTSA) issued Federal Motor Vehicle Safety Standard 127 (“FMVSS 127”), which establishes performance requirements for automatic emergency braking systems for light vehicles and set a deadline for automakers to implement certain crash mitigation features by September 1, 2029. Subsequent regulatory action, litigation, and a freeze imposed by the Trump Administration have left automakers in limbo as to whether and when this rule will take effect and in what form. Without some action, however, the September 2029 deadline set by NHTSA looms large.

Genesis of FMVSS 127

The Bipartisan Infrastructure Law, 49 U.S.C. § 30129, enacted in November 2021, requires the U.S. Department of Transportation (DOT) to promulgate a rule “to establish minimum performance standards with respect to crash avoidance technology” and set an effective date and any phasing-in requirements for that rule to take effect. In adopting FMVSS 127 in May 2024, NHTSA required most Original Equipment Manufacturers (“OEMs”) to implement certain crash mitigation features by September 1, 2029—including automatic emergency braking (AEB), pedestrian AEB (PAEB), and forward collision warning (FCW) systems on all new passenger cars and light trucks weighing 10,000 pounds or less—and estimated the rule would save at least 360 lives and prevent more than 24,000 injuries annually.

Under FMVSS 127, vehicles must be capable of achieving (1) full collision avoidance with a lead vehicle, defined as a test vehicle facing the same direction and preceding a subject vehicle within the same travel lane, at speeds up to 62 mph; (2) detect pedestrians in both daylight and darkness;  and (3) automatically engage braking up to 90 mph for imminent vehicle collisions and up to 45 mph when a pedestrian is detected. Small-volume manufacturers, final-stage manufacturers, and alterers (persons, who before the first retail sale, modify a certified vehicle by the addition, substitution, or removal of components) are also subject to the AEB requirement but were afforded an extended compliance period, with covered vehicles required to incorporate a compliant AEB system no later than September 1, 2030.

Headwinds for FMVSS 127 Since Adoption

In June 2024, shortly after NHTSA announced the final rule, the Alliance for Automotive Innovation (“Auto Innovators”) and a number of manufacturers petitioned NHTSA to reconsider the rule. NHTSA reviewed these petitions and in November 2024 issued a revised final rule that granted portions of these petitions but left FMVSS 127 largely unchanged.  In a November 2024 statement, Auto Innovators’ president John Bozzella called NHTSA’s decision “a disastrous decision by the nation’s top traffic safety regulator that will endlessly – and unnecessarily – frustrate drivers; will make vehicles more expensive; and at the end of the day…won't really improve driver or pedestrian safety.”

On January 17, 2025, Auto Innovators filed a petition in the U.S. Court of Appeals for the D.C. Circuit seeking judicial review of FMVSS 127 under the federal Administrative Procedures Act. Only three days later, the incoming Trump Administration on January 20, 2025 implemented a regulatory freeze directing agencies to, among other things, consider postponing the effective date of rules that had not yet taken effect and conduct a further review. On February 24, 2025, the DOT filed an unopposed motion to hold this appeal in abeyance pending a review of FMVSS 127; that motion was granted four days later and the matter has remained in abeyance ever since.

Notwithstanding the regulatory freeze, the September 2029 compliance deadline for manufacturers remains in place. The D.C. Circuit litigation and any potential NHTSA rulemaking activity are proceeding side by side, and their outcomes will shape the compliance landscape for the next decade. Most recently, on March 23, 2026, the DOT announced in a status report filed with the D.C. Circuit that “the Department is currently preparing a notice of proposed rulemaking that would, if finalized, amend certain aspects of the rule.” The proposed rule change would extend the compliance lead time for OEMs by two years to provide “more time to achieve challenging aspects of the standard.”

In the meantime, the appellate challenge to FMVSS 127 remains in abeyance, and unless the proposed rule change is adopted, the current September 2029 compliance deadline remains in place. For automakers, the only certainty is continued uncertainty about their near-term regulatory obligations with respect to automatic emergency braking systems.