Federal Motor Carrier Safety Administration (FMCSA) Grants a Crucial Regulatory Exemption for Autonomous Trucks

On October 9, the Federal Motor Carrier Safety Administration (FMCSA) took a significant step toward enabling the large-scale deployment of driverless heavy trucks on public roads in the United States. The agency granted autonomous motor carriers a five-year exemption from the regulatory requirement that a truck that stops on the side of the road must put warning triangles on the ground. This seemingly mundane requirement has posed a potential roadblock (so to speak) to the operation of autonomous trucking. The recent exemption, which follows years of petitions and litigation, offers a solution.

The Rise of Autonomous Trucking

Though robotaxis have gotten the most attention, heavy trucking is also a major growth area for autonomous mobility. Autonomous freight has the potential to address driver shortages and turnover, especially on the most isolated and difficult routes; it can save labor costs, as driver wages and benefits make up more than 40% of a truck’s operating costs per mile; it allows for higher asset utilization due to the hours-of-service limits that apply to human drivers; and can potentially improve safety. Numerous companies, with a variety of business models, have entered the autonomous trucking space in recent years.

The Warning Triangle Regulations and Their Application to Autonomous Trucks

Longstanding Federal Motor Carrier Safety Regulations (FMCSRs) provide that whenever a commercial motor vehicle is stopped on a public road or the road’s shoulder, the driver must place warning devices on the ground as a signal to other drivers. These warning devices usually take the form of reflective triangles.

Placing warning triangles on the road is usually a simple operation for a vehicle with a human behind the wheel—albeit one with its own risks. But it is a much more difficult endeavor for a vehicle that has no human occupant, especially because the regulations normally require two of the warning devices to be placed about 100 feet from the vehicle.

The Exemption Application Process and Ensuing Litigation

Federal law authorizes FMCSA—acting by designation from the Secretary of Transportation—to grant an exemption from compliance with an FMCSR if the agency determines that “the waiver is likely to achieve a level of safety that is equivalent to, or greater than, the level of safety that would be obtained in the absence of” the waiver or exemption.

The warning-device requirement for commercial motor vehicles has created operational challenges for the emerging technology of autonomous trucks. Accordingly, in March 2023, two autonomous technology companies—Aurora Operations, Inc. and Waymo LLC—petitioned for an exemption from several of the warning device requirements.

As an alternative to the ground-based warning devices, the companies proposed that commercial motor vehicles equipped with autonomous driving systems be permitted to use cab-mounted flashing lamps. In support of the exemption, the applicants submitted two studies on the safety of cab-mounted warning beacons.

In December 2024, FMCSA denied this initial exemption request. The agency concluded that the applicants had not provided sufficient detail on the proposed alternative cab-mounted beacons, and that the studies they had submitted “provided insufficient data to demonstrate an equivalency in driver responses.”

FMCSA also noted at the end of its denial that “the Agency may accept a resubmission of an exemption application that has been denied, provided that the applicant can reasonably address the reason for the denial.”

The following month, Aurora sued FMCSA, filing a petition for review of the decision denying the exemption. The petition alleged that “FMCSA arbitrarily and capriciously denied the Application contrary to record evidence and without adequate, reasoned explanation. FMCSA’s decision stifles safety innovation and would impede the development of the autonomous trucking industry for no valid or lawful reason.”

Later in 2025, FMCSA, under new leadership, took another look at the issue. That October, FMCSA granted Aurora the first of a series of a limited, three-month waivers from the warning device regulations, subject to various terms and conditions. Aurora dropped its lawsuit shortly thereafter.

In the most recent such waiver, the agency explained that “FMCSA has now determined that it is in the public interest to issue a waiver, limited in scope and circumstances, that is likely to achieve a level of safety that is equivalent to, or greater than, the level of safety that would be obtained in the absence of the waiver.” The waiver was granted to Aurora, as well as “other motor carriers operating Level 4 ADS-equipped [commercial motor vehicles that] provide written notification to FMCSA and certify compliance with the waiver’s terms and conditions.”

The Five-Year Exemption

In April 2026, Aurora submitted a renewed application for a five-year exemption from the warning-device requirements, which would replace the successive three-month waivers. The application relied, in part, on evidence from the use of the cab-mounted beacons in vehicles that Aurora operated under its earlier short-term waivers. FMCSA received over 400 public comments in response to the application.

On October 9, FMCSA granted Aurora’s exemption application, providing long-term regulatory relief to Aurora. The decision allowed other motor carriers that operate commercial motor vehicles equipped with SAE Level 4 automated driving systems to also use the exemption if they notify FMCSA in writing before commencing operations and provide specified information and affirmations.

Notably, the exemption decision did not significantly criticize the agency’s previous denial. Rather, the decision relied on new information provided in the exemption application and the limitations of the exemption that the agency was granting. For example, “the 2024 denial also noted a lack of sufficient details about the proposed alternative devices. This exemption resolves that ambiguity by including” additional technical specifications for the cab-mounted beacons. The decision also relied on evidence from Aurora’s 500,000 miles of operations under one of its three-month waivers. The agency observed that “all data collected under the waiver indicated that Aurora’s operations with the cab-mounted beacons did not degrade highway safety.”

The agency also took another look at the two studies that had been submitted with the 2023 exemption application. FMCSA noted that the evidence from one of the studies showed that under most tested scenarios that compared driver reaction to the cab-mounted beacons with reactions to warning triangles, “motorists initiated their first evasive response (such as a lane change or slowing down) further back from the trailer when exposed to the beacons compared to the triangles. The study concluded that the beacons performed equivalently to the deployment of the triangles.” Likewise, the second study “highlighted specific areas where beacons outperformed triangles, noting that nighttime beacon exposure elicited earlier braking and slower, safer passing speeds.”

The exemption has several notable terms and conditions, including:

• Operations under the exemption can only take place on roadways within the vehicle’s validated Operational Design Domain.
• Certain types of commercial vehicles, including school buses and other passenger vehicles, vehicles that carry hazardous materials, and certain especially lengthy combination vehicles are not covered by the exemption.
• The cab-mounted beacon must meet certain specifications, including height from the ground, color, photometric performance, flash pattern, and power source redundancy.
• The beacon must activate as soon as possible after the vehicle stops, and always within five minutes (as opposed to the FMCSR’s ten-minute requirement for placing warning triangles).
• Each motor carrier operating under the exemption must report crashes while the cab-mounted warning beacons are activated or should have been activated.
• Exempted carriers must provide annual reports with information on their operations.

Takeaways:

• The exemption creates big opportunities for the deployment of autonomous freight. At the same time, it comes with significant compliance and reporting requirements, which companies should examine closely and, where necessary, work with experienced counsel.
• This exemption is just one of many recent actions by the Department of Transportation aiming to promote autonomous technology. The National Highway Traffic Safety Administration (NHTSA), which regulates vehicle safety, has also taken various actions on this front, including by issuing its own regulatory exemptions to autonomous vehicle companies, and the Secretary of Transportation has been very vocal about the Administration’s “National AV Strategy.”
• Though not certain, the recent exemption from the FMCSRs that require warning devices could eventually be followed by action to modify the standards themselves to allow for cab-mounted beacons as an alternative to warning triangles. In the past several years, NHTSA has moved to update Federal Motor Vehicle Safety Standards to account for vehicles with no human driver, and FMCSA could well follow.
• While federal regulators are taking steps to enable the deployment of autonomous trucks, many state and local restrictions remain. Autonomous freight companies will want to understand those obligations and engage with state and local regulators and policymakers when necessary.

This post is as of the posting date stated above. Sidley Austin LLP assumes no duty to update this post or post about any subsequent developments having a bearing on this post.