Autonomous Trucks: Who Places the Warning Triangles When There’s No Driver?

A truck stops on the highway shoulder. Traffic keeps moving, and someone must warn approaching drivers of the hazard. For a truck driver, placing emergency warning devices is part of the procedure. But how does that happen when there is no person behind the wheel?

The Federal Motor Carrier Safety Administration (FMCSA) granted an exemption to Aurora and other operators of commercial vehicles equipped with Level 4 automated driving systems that notify the agency beforehand and meet its conditions. Published on October 9, the exemption is effective from October 7, 2026, through October 7, 2031. It permits cab-mounted warning beacons in place of traditional warning devices.

What the Standard Procedure Requires

Federal regulations require drivers to immediately activate hazard warning lights when a commercial vehicle stops on the roadway or shoulder for reasons other than necessary traffic stops. Required warning devices must be placed as soon as possible, within ten minutes.

Placement depends on the road. On divided or one-way highways, devices are positioned toward approaching traffic. Near curves or hillcrests, distances are adjusted to provide advance warning.

Warning Beacons—with Conditions

The exemption requires forward- and rearward-facing amber lights, redundant power sources, and activation as soon as possible, within five minutes. The beacons must remain flashing throughout the stop, alongside the vehicle’s standard hazard lights.

Operations are restricted to the automated system’s validated operating domain. Passenger and hazardous materials transportation are excluded, and operators must report specified crashes and equipment failures.

The Safety Debate

FMCSA determined that the alternative would likely provide an equivalent or greater level of safety. However, the official record includes objections concerning curves, visibility, and trailers potentially blocking the beacons. The exemption does not remove the general warning-device requirements for human-driven trucks.

The case illustrates a practical challenge of automation: driving is only part of the job. Handling a roadside stop and warning approaching motorists also requires a safe response.

Official Sources

• FMCSA / Federal Register: Exemption decision for Aurora and other operators, published October 9, 2026. Document 2026-20734; docket FMCSA-2026-0958.
• eCFR: 49 CFR § 392.22 — Emergency signals; stopped commercial motor vehicles.