Yes. A marker light that is out on a commercial motor vehicle is a DOT violation whenever the lamp is one your vehicle is required to have. Under 49 CFR 393.9(a), every lamp required by the federal lighting regulations must be capable of operating at all times, with no exception for daytime driving and no grace period.1eCFR. 49 CFR 393.9 – Lamps Operable, Prohibition of Obstructions of Lamps and Reflectors One dead side marker on an otherwise well-lit trailer is enough for a citation.
Whether a specific lamp is “required” depends on the vehicle. The table in 49 CFR 393.11 sets out which clearance lamps, side marker lamps, and identification lamps a truck, tractor, or trailer must carry based on width and length. If the lamp appears on that table for your vehicle, it has to work.2eCFR. 49 CFR 393.11 – Lamps and Reflective Devices
Will It Put You Out of Service?
No. Under CVSA’s enforcement guidance, inoperable marker lights, clearance lamps, and identification lamps are written up as standard violations, not out-of-service conditions. The lighting failures that shut a truck down at the roadside are the ones tied directly to collision avoidance: headlamps, tail lamps, stop lamps, and turn signals on the rearmost unit.3Commercial Vehicle Safety Alliance. Operational Policy 14 – Enhancing Roadside Inspection and Enforcement Data Uniformity
You’ll get paperwork, not a padlock. But if the inspector finds the marker light problem sitting next to other maintenance defects, expect the rest of the vehicle to get a closer look.
What the Fine Can Be
A marker light violation falls into the non-recordkeeping category of Federal Motor Carrier Safety Regulation penalties. The statutory maximum is $19,246 per violation for a carrier and $4,812 per violation for a driver cited individually.4eCFR. Appendix B to Part 386 – Penalty Schedule: Violations and Monetary Penalties
Those are ceilings, not typical fines. A single dead marker light at a roadside inspection rarely draws the maximum. The numbers climb for repeat offenders and carriers with a pattern of maintenance failures, and FMCSA adjusts the caps annually for inflation.5Federal Motor Carrier Safety Administration. Revisions to Civil Penalty Amounts, 2025
The Longer-Lasting Cost: Your CSA Score
The dollar figure is often the smaller problem. FMCSA logs every roadside violation in its Safety Measurement System, and a marker light citation lands in the Vehicle Maintenance BASIC. It stays on the carrier’s record for 24 months.6Federal Motor Carrier Safety Administration. Vehicle Maintenance BASIC Factsheet
Each violation carries a severity weight that raises the carrier’s percentile ranking against similar-sized peers. A higher percentile can trigger warning letters, targeted investigations, and more frequent inspections. On a small fleet, a handful of lighting citations is enough to push the Vehicle Maintenance BASIC into intervention territory. The only ways out are time without new violations or clean inspections that dilute the record.
When a Burned-Out Marker Light Is Not a Violation
Two situations keep you clear.
The first is auxiliary lighting. Section 393.9 explicitly says that auxiliary or additional lamps do not have to work at all times. If your rig carries extra marker lights beyond what 393.11 requires, a dead bulb among those extras is not a citable defect. The rule reaches only the lamps the regulation actually mandates for your vehicle type.7eCFR. 49 CFR 393.9 – Lamps Operable, Prohibition of Obstructions of Lamps and Reflectors
The second is partial LED failure. When individual diodes inside an LED marker lamp burn out but the lamp still meets visibility requirements as a whole, there is no violation. The standard is whether the lamp functions adequately, not whether every diode is lit.3Commercial Vehicle Safety Alliance. Operational Policy 14 – Enhancing Roadside Inspection and Enforcement Data Uniformity
Catching It Before an Inspector Does
Federal regulations require the driver to confirm the vehicle is in safe operating condition before driving and to review the previous driver’s vehicle inspection report for any listed defects.8eCFR. 49 CFR 396.13 – Driver Inspection
Marker lights sit along the upper edges and sides of the vehicle, where a headlight-and-taillight check misses them. Walk the vehicle with the parking lights on. Two minutes around the trailer catches the bulbs and connections that would otherwise show up at a scale house, and it satisfies the pre-trip duty at the same time.