Trucking officials set minimum for LED lights
Fifteen percent is the minimum number of working diodes needed for an LED taillight to be considered legal, or will be if a long-sought safety minimum is approved by trucking officials and vehicle inspectors.
Members of an industry group have been grappling with the issue for several years and finally settled on the 15% figure at a September meeting. It’s part of a recommended practice that could be approved by the group’s parent organization next March, then possibly adopted by a consortium of truck safety inspectors later in 2026.
Only 15% of working diodes would still emit enough red light to be seen from behind a trailer or truck and thus remain legal, the group decided. But “the recommended practice also suggests that a fleet immediately replace a display if more than one LED element is found to be inoperative, and that the fleet may want to set its own maintenance standard to higher than 15% to reduce the chances of a violation during a roadside inspection,” explained Jack Legler, technical director of American Trucking Associations’ Technology & Maintenance Council, or TMC.
Rear lamps made of light-emitting diodes raised questions among inspectors not long after they were introduced in the early 1990s. That’s because a typical red LED tail lamp consists of five or more diodes and they seldom burn out all at once, as usually happens with incandescent bulbs. And no federal regulation states when an LED lamp has become dim enough to be officially failed, so it was up to inspectors to make the call.
The group making the recommendation consists of fleet managers and representatives of light-equipment manufacturers who are also members of TMC, which will publish the final document. The other interested body is the Commercial Vehicle Safety Alliance, composed of state and provincial safety inspectors from the U.S., Canada and Mexico. It asked TMC to establish a quantifiable standard that inspectors could point to in issuing a citation, said Kerri Wirachowsky, CVSA’s director of inspection programs. She has been monitoring the TMC group’s deliberations.
The TMC group, which first debated the issue, initially decided on 50%, but that was dropped because it was deemed too stringent. The far-lower 15% figure is reasonable, members of the group concluded, because a current federal safety reg that says a taillight only needs to be visible from 50 feet to be legal. The current reg does not require a minimum measurable intensity; it only requires that an inspector can see the light.
With the new 15% figure, commercial vehicle inspectors could do the arithmetic and come up with an objective decision, Wirachowski said. That’s assuming CVSA approves of the TMC group’s proposed recommended practice, or RP, which will be voted on by all TMC members in January, then finalized in March.
“The Vehicle Committee at CVSA will have to have that discussion once the RP passes at TMC,” Wirachowski said. LL