The NHTSA published an NPRM in the June 26, 2026 Federal Register (F.R. Vol. 91, No. 122; NHTSA-2026-0728) which would distinguish how the braking regulation applies to vehicles with and without manually operated driving controls. The updated FMVSS 135 to accommodate Automated Driving Systems (ADS)-equipped vehicles is intended to clarify definitions, tell-tale requirements, performance requirements, and test procedures in the Standard and remove sections that are no longer relevant. The stopping distance performance requirements, primary safety purpose of the Standard, would still apply to all subject vehicles. This rulemaking would remove unnecessary regulatory burdens and costs without detriment to vehicle safety.
Though these vehicles currently are not available for consumer purchase, there is considerable testing, development, and validation of these vehicles, as well as localised deployment by manufacturers and rideshare operators. Vehicle automation technology has the potential to reduce roadway crashes and fatalities while increasing mobility. As the technology is still maturing and many of the potential benefits are yet to be realised, the NHTSA is engaging in a process to modernise existing FMVSS.
The NHTSA proposes to revise the current requirements that all light vehicles contain hand- or foot-operated brake controls, removing those requirements for vehicles designed never to be operated by a human. For vehicles without manually operated driving controls, the NHTSA proposes application of existing performance requirements through alternative test procedures. The proposed changes also include language modifications, corrections of typographical errors, and removal of outdated information to clarify the braking performance requirements for all subject vehicles. The NHTSA is not proposing changes to any stopping distance requirements in FMVSS 135. Regardless of the manner of brake control application, the brake systems must be capable of safely stopping the vehicle, as already required by the Standard. This rulemaking would remove unnecessary regulatory burdens and costs with no negative impact to vehicle safety. For ADS-equipped vehicles that contain manually operated driving controls, the existing requirements of the Standard would still apply.
Importantly, this proposal is intended to remove unintended design barriers that exist in FMVSS 135 and maintain existing brake performance requirements for designs that are newly enabled. The proposal would ensure that ADS-equipped vehicles without manually operated driving controls can stop within an appropriate distance once brake controls are actuated. However, whether the vehicle's brakes are actuated appropriately given a specific driving scenario is an independent question relating to ADS performance. To this end, the NHTSA is in the process of developing safety performance tests for ADS-equipped vehicles, which would be implemented in a separate Standard. As with any ADS-equipped vehicle, the NHTSA will not hesitate to use its strong and broad defect enforcement authority to address unsafe ADS performance if the proposal is finalised.
The NHTSA is requesting comments for specific areas to ensure that functions, test results, definitions are comparable among the various ADS- and non-ADS-equipped vehicles. FMVSS currently requires independent manual controls for activation of the service brakes and the parking brake. In an ADS-equipped vehicle without manually operated driving controls, the ADS would perform the driving task and any vehicle occupants would be passengers. The ADS would operate the service brakes and the parking brake without the need for a foot-operated service brake pedal, or a hand- or foot-operated parking brake control. The NHTSA seeks comment on potential consequences of removing the requirements for hand- and foot-operated brakes in ADS-operated vehicles.
For vehicles without manually operated driving controls, The NHTSA also proposes to require that the service brake control and the parking brake control are activated by on-board systems. This clause precludes the use of an external command system in which the braking signal can only be sent from outside the vehicle, rather than being directed by an on-board ADS. Further, in an ADS-operated vehicle, a control that is designed for operation by a vehicle occupant to direct the vehicle to a stop and is not the primary braking control would not be considered part of the service or parking brake controls. The NHTSA seeks comment on other considerations and concerns related to ADS vehicle operation (definition for service brake control and potential alternatives, the definition for stopping distance to clarify the measurement for vehicles with and without manually operated driving controls, proposed definition does not modify how the stopping distance is determined for vehicles that have a service brake pedal, stopping distance is still the distance travelled by a vehicle from the point of initial application of force to the service brake control to the point at which the vehicle reaches a full stop, definitions and functions of tell-tales and warnings, plus others).
FMVSS may not become effective before the 180th day after the Standard is prescribed or later than one year after it is prescribed. However, NHTSA may provide a different effective date after finding, for good cause shown, that a different effective date is in the public interest. It is in the public interest for this proposed rule, if adopted, to be effective immediately. This proposed rule clarifies existing requirements and removes unnecessary regulatory requirements for ADS-equipped vehicles without manually operated controls. There is no need for lead time for regulated entities to comply with this proposed rule. The NHTSA seeks comment on whether the rule could be made effective within a time period shorter than 180 days or upon publication of any Final Rule.
The NHTSA seeks public comment on the proposed changes, including the proposed exceptions to the requirements for hand- and foot-operated brake controls, the proposed definitions, the proposed revisions to the test procedures, the proposed tell-tale requirements for vehicles without manually operated driving controls, and the proposed removal of the friction type parking brake requirement. The NHTSA will submit a redline-change version of the Standard in its entirety to the docket to facilitate review of the proposed changes.
The comment period for this Notice of Proposed Rulemaking (NPRM) closed on July 27, 2026.
The NPRM is available on InterRegs.NET for our US Federal subscribers and is also available at Selectregs.com.