Rear-end collision warning lamps from Grote: FMCSA reopens comments on the exemption request

Where things stand on October 20, 2026: Grote Industries, LLC has asked FMCSA for a five-year exemption from 49 CFR §393.25(e), which, in FMCSA's words, generally requires exterior lamps on commercial motor vehicles (CMVs) to be steady-burning. If granted, the exemption would allow motor carriers to operate CMVs equipped with auxiliary warning lamps controlled by Grote's Rear-End Collision Warning (RCW) system. On October 20, 2026, FMCSA published a notice that makes new information from Grote available and asks for comments on it. Comments must be received on or before November 19, 2026. FMCSA has not decided on the exemption request.

What Grote asked for

• December 10, 2025. Grote applied for the exemption on behalf of motor carriers seeking to use auxiliary warning lamps with its RCW system. The application described one or more auxiliary lamps on the rear or sides of a CMV or trailer, and a rear-facing radar that calculates the time-to-collision (TTC) of vehicles approaching from behind. It also contemplated using the system on the side of a CMV for side-impact protection during parking maneuvers.
• February 9, 2026. FMCSA published a notice of the application and requested public comment.
• March 4, 2026. FMCSA extended the comment period by 60 days, through May 10, 2026, after the Commercial Vehicle Safety Alliance (CVSA) requested more time to review the application.

In the application, Grote said the RCW signal circuit would activate when TTC was less than or equal to a threshold corresponding to a substantial risk of an impending collision, typically between 2.1 and 4.0 seconds. It proposed two possible lamp sequences:

1. red lamps flashing between four and sixteen times during a four-second period, then burning steady red while the RCW signal remained active; or
2. amber lamps operating as SAE J595 Class 3 or Class 2 strobe lamps for up to four seconds, then burning steady red while the RCW signal remained active.

Grote also said the auxiliary lamps could be used in combination with brake and marker signal circuits.

What commenters raised

During the comment period, interested parties raised, among other issues, the relationship between the RCW system and forward collision warning technology, the meaning the lamps would convey to following motorists, and the proposed change from flashing or strobing lamps to a steady-burning red indication. CVSA was concerned that following motorists could interpret steady-burning red lamps as a sign that the CMV was braking, and recommended that the system not change from flashing amber to steady-burning red for a warning unrelated to brake application.

The new information from Grote

After the comment period closed, FMCSA staff asked Grote to clarify the design and operation of the system. FMCSA placed in the docket a memorandum summarizing the meeting between its staff and Grote, titled Ex Parte Communication with Grote Industries, LLC Regarding Rear-End Collision Warning Lamp System. It includes a chart from Grote showing how the RCW system works and how it interacts with the brake-activated lamp function. According to the notice:

Color and sequence.

Grote clarified that when operating as part of the RCW system, the auxiliary warning lamps pulse in amber for up to four seconds with each activation of the RCW signal circuit and do not transition to a steady-burning red indication.

Grote explained that the change from amber pulsing to steady-burning red is associated with its brake-activated auxiliary pulsating lamp function, not with the RCW warning function. FMCSA notes that this differs from the original application and the February 9, 2026 notice, which said the lamps would change to steady-burning red after the initial flashing or strobing sequence while the RCW signal remained active.

Braking takes precedence. The RCW system uses the same auxiliary lamps as Grote's brake-activated auxiliary pulsating lamp system. When an RCW event and a braking event occur at the same time, Grote said the brake-activated function takes precedence: if the service brakes are applied during an RCW event, the lamps change from the RCW sequence to the brake-activated sequence. Any steady-burning red indication would therefore be associated with brake application, not with the RCW warning. The original application did not describe that priority.

Radar. Grote said the system uses a self-contained, rear-facing radar that can detect approaching vehicles at distances of approximately 200 meters, continuously evaluates their relative motion and calculates TTC. When the calculated TTC reaches the programmed activation threshold, the system automatically turns on the amber warning lamps. Grote said the system does not require the driver to activate or otherwise interact with it, and that the radar would not interfere with other radar-based vehicle detection systems.

Which vehicles. Grote said it intends the exemption to apply to all CMVs. On combination vehicles with more than one trailing unit, including doubles and triples, the system would be installed and operated on the rear-most unit.

The comment period

Comments must be received on or before November 19, 2026, identified by docket FMCSA-2026-0100. The notice limits what FMCSA will consider:

Comments submitted in response to this notice must be limited to addressing any relevant information summarized in this notice and in the Memorandum to the Docket identified above. Comments addressing other matters will not be considered by FMCSA.

The notice lists four ways to submit comments: the Federal eRulemaking Portal (regulations.gov), mail, hand delivery or courier, and fax. DOT posts comments without change, including any personal information in them. Comments received after the closing date will be filed in the public docket and considered to the extent practicable.

What happens next

According to the notice, FMCSA reviews the application, the safety analyses and the public comments, and determines whether granting the exemption would likely achieve a level of safety equivalent to, or greater than, the level that would be achieved without it. FMCSA must publish its decision (§381.315(b)). If the exemption is granted, that notice will identify the provisions from which the exempted party will be exempt, the effective period, and all terms and conditions (§381.315(c)(1)). If it is denied, the notice will explain the reason (§381.315(c)(2)). An exemption may be renewed (§381.300(b)). We will update this article when FMCSA publishes its decision.

Sources

• FMCSA, Parts and Accessories Necessary for Safe Operation; Application for an Exemption From Grote Industries, LLC, notice of availability of supplemental information; request for comments, 91 FR 66385 (October 20, 2026).
• 49 CFR §393.25, the section the exemption request concerns.
• 49 CFR §381.315, the exemption procedure the notice cites.
• Docket FMCSA-2026-0100, regulations.gov.