Grote clarifies how its rear-collision warning lamps would work; FMCSA reopens comments to November 19

The notice, published in the Federal Register on October 20, 2026, puts new information from Grote into docket FMCSA-2026-0100. The key change concerns how the lamps would signal to the driver behind.

The request

Federal rules at 49 CFR 393.25(e) generally require a truck's exterior lamps to be steady-burning. On December 10, 2025, Grote asked FMCSA for a five-year exemption so motor carriers could run auxiliary warning lamps controlled by its Rear-End Collision Warning (RCW) system.

The system uses rear-facing radar to estimate how many seconds remain before an approaching vehicle would hit the truck. When that time-to-collision drops to a set threshold, the auxiliary lamps light up as a warning. Grote's application put the threshold typically between 2.1 and 4.0 seconds. The application also mentioned possible side-mounted use to guard against side impacts while parking.

FMCSA first took comments starting February 9, 2026. In March it extended the comment period to May 10, 2026, after the Commercial Vehicle Safety Alliance asked for more time.

The concern

As originally described, the lamps would flash red or strobe amber for up to four seconds and then stay steady red as long as the collision risk continued.

Commenters asked how the system relates to forward collision warning technology, what the lamps would mean to drivers behind the truck, and why a flashing warning would switch to steady red. CVSA said following drivers could read a steady red lamp as a sign that the truck was braking. It recommended that the system not switch from flashing amber to steady red for a warning that has nothing to do with braking.

What Grote now says

After the comment period closed, FMCSA staff met with Grote. According to the agency's summary, Grote said:

• In RCW mode, the auxiliary lamps pulse amber for up to four seconds each time the system is triggered, and they do not change to steady red.
• The switch from pulsing amber to steady red belongs to Grote's separate brake-activated auxiliary lamp function, which uses the same lamps.
• If the brakes are applied during a collision warning, the brake function takes priority. Any steady red signal would therefore mean the truck is braking.
• The radar is self-contained, can detect approaching vehicles about 200 meters away, needs no action from the driver, and would not interfere with other radar-based detection systems.
• The exemption is meant to cover all commercial motor vehicles. On doubles and triples, the system would be installed only on the last trailer.

FMCSA notes that the lamp behavior now described differs from both the original application and its February notice.

A memo summarizing the meeting, including a Grote chart showing how the RCW and brake functions interact, is in the docket. It is titled "Ex Parte Communication with Grote Industries, LLC Regarding Rear-End Collision Warning Lamp System."

How to comment

Comments are due November 19, 2026, at regulations.gov under docket FMCSA-2026-0100, or by mail, hand delivery or fax as listed in the notice. FMCSA will consider only comments on the new information described in this notice and the docket memo.

FMCSA has not yet decided whether to grant the exemption.