Required Lights on a Truck and Trailer
Which lamps and reflectors a commercial truck and trailer must have, where they go, and why one dead marker light is the easiest violation to avoid.
Lighting violations are among the most common items written at roadside inspections, and they are the cheapest defects on the truck. A marker light costs less than lunch. The problem is that most drivers do not know exactly which lamps are required, so a missing one on the side of a trailer goes unnoticed until an inspector walks past it with a clipboard. Knowing the list turns the walkaround into a real check.
Here is what the federal rules require on a truck and trailer, in plain terms, and what to look for.
The tractor
- Headlamps, two, with high and low beam.
- Front turn signals, two, amber.
- Front clearance lamps, two, amber, at the top corners on wide vehicles.
- Front identification lamps, three amber lamps in a row at the top center, on vehicles over a set width.
- Side marker lamps, amber at the front and red at the rear, with intermediate amber markers on long vehicles.
- Rear: two tail lamps, two stop lamps, two rear turn signals, a license plate lamp, two rear clearance lamps and three red identification lamps on wide vehicles, and backup lamps.
- Reflectors, amber at the sides toward the front and red at the sides toward the rear and on the rear, or reflective tape in the places it is required.
The trailer
- Front clearance lamps, two, amber, at the top front corners.
- Side marker lamps and reflectors, amber toward the front, red toward the rear, with intermediate amber markers on trailers over a set length.
- Rear: two tail lamps, two stop lamps, two turn signals, a license plate lamp, two red clearance lamps, and three red identification lamps in a row at the top center.
- Rear reflectors and the conspicuity tape pattern along the sides and across the rear, on trailers that require it.
- The retroreflective tape has to be present, intact, and not painted over or obscured by dirt.
The identification lamps, the three-in-a-row set, are the ones drivers most often cannot name. They are required on wide vehicles at the front of the tractor and the rear of the trailer, and inspectors look for them.
What counts as a violation
A required lamp that does not work, is missing, is the wrong color, or is obscured is a violation. A cracked lens that lets white light show through a red lamp is a violation. Conspicuity tape that is peeling or missing over a length is a violation. Most lighting violations are not out-of-service by themselves, but stop lamps, tail lamps, turn signals, and headlamps at night are the ones that can put a truck out of service, and a truck with several lighting defects tells the inspector to look harder at everything else.
One dead lamp is a violation. Several is a pattern, and it invites a full inspection. Fix them as they fail, not once a year.
Why lights fail
On modern trucks and trailers, LED lamps rarely burn out. They fail because water gets into the housing or the connector, because the ground is bad, or because the harness has chafed through somewhere along the frame. A whole side of markers out is a ground or a harness break, not a row of dead lamps. A lamp that flickers on rough roads is a connector. We walked through the diagnosis in Trailer Lights Out: Working Backward From the Plug and the tractor side in Truck Electrical Problems: When the Lights Go Out.
The walkaround
- With the lights on, walk the full circle. Count the markers on each side of the trailer. Look at the three identification lamps front and rear.
- With a helper, check stop lamps, both turn signals, and the four-way flashers.
- Look at every lens for cracks and every housing for fog or water inside.
- Walk the conspicuity tape. Peeling, missing sections, or paint on it.
- Check the reflectors. They are part of the requirement and they get knocked off.
Fixing lighting in the yard
Lamps, pigtails, grounds, harness repairs, and conspicuity tape are all yard jobs, and they are the kind of thing that gets done on a scheduled visit alongside the rest of the list. A fleet that sends every truck out with every lamp working has removed the easiest violation from the table. It is a small part of a fleet service visit and it is on the list for our annual inspection prep walkthrough.
Frequently asked questions
Are the three lights on top of the cab required?
On vehicles over the specified width, yes. They are identification lamps and they are required front and rear.
Is a cracked tail light lens a violation?
If it lets white light show or affects the color or visibility of the lamp, yes.
Can I add extra lights to a truck?
Additional lamps are allowed within limits on color, placement, and whether they impair the required lamps. Flashing or colored lamps that could be mistaken for emergency vehicles are not.
Can a mobile crew fix trailer lights on the road?
Yes. Lamps, connectors, and harness repairs are done on the shoulder or in the yard.
Lights out on a truck or trailer anywhere on the panhandle? Call Duckett Roadside Repair at (850) 495-0366. Dispatch is answered 24 hours a day.