Truck cab clearance lights mark the top corners and edges of your cab so other drivers know how wide and tall your truck is

Clearance lights are small marker lights mounted on the highest points of your truck's cab — typically at the front top corners and sometimes along the roof line. Their job is to show other drivers the width and height of your vehicle, especially at night or in poor visibility. They are required by federal law on trucks over a certain size, and they run on your truck's electrical system.

These lights are different from brake lights, turn signals, or headlights. They stay on whenever your truck is in operation and serve a safety purpose: they help prevent other vehicles from misjudging your truck's dimensions and hitting you, particularly in lane changes, passing, or when you are parked on the roadside.

Key Takeaways

  • Clearance lights are required on trucks with a gross vehicle weight rating (GVWR) over 10,000 pounds and must be amber on the front and red on the back.
  • These lights mount on the highest points of the cab to show width and height, and they must be visible from 500 feet away in normal daylight.
  • Clearance lights run continuously when the truck is in operation and are wired into your truck's main electrical system.
  • A burned-out clearance light is a safety issue and a violation that can result in a citation during a roadside inspection.

Federal requirements for cab clearance lights

The Federal Motor Carrier Safety Administration (FMCSA) sets the rules for clearance lights on commercial trucks. If your truck has a GVWR over 10,000 pounds, you must have clearance lights. The specific requirements are that front clearance lights must be amber, rear clearance lights must be red, and they must be visible from at least 500 feet away in daylight conditions.

Most trucks require at least two clearance lights on the front (one on each top corner of the cab) and two on the rear. Some larger trucks or those with certain configurations may need additional lights along the roof line or on the sides. Your truck's manufacturer typically installs these during production, but if you own an older truck or have modified your cab, you may need to verify that your setup meets current standards.

The lights must be mounted so they are not blocked by cargo, equipment, or other parts of the truck. If your clearance lights are obscured, you are in violation even if the lights themselves are working.

How clearance lights are wired and powered

Clearance lights are hardwired into your truck's electrical system and draw power from your main battery through a dedicated circuit. They typically have their own fuse or breaker to protect the wiring. The lights are controlled by the ignition switch, meaning they turn on when you start the truck and turn off when you shut it down.

Because clearance lights run continuously while the truck is operating, they draw a small but steady amount of power. On most modern trucks, this is not a significant drain, but on older vehicles or those with weak batteries, running clearance lights for extended periods can contribute to battery drain if the alternator is not keeping up.

If a clearance light burns out, the circuit usually remains intact — only that individual bulb stops working. You can replace the bulb yourself in most cases by accessing the light fixture from inside the cab or from the exterior, depending on your truck's design. Check your owner's manual for the specific bulb type and replacement procedure for your model.

Checking and maintaining your clearance lights

You should inspect your clearance lights regularly as part of routine truck maintenance. Walk around your truck during daylight and look at each light to make sure the lens is clean and not cracked. At night, turn on the truck and have someone stand in front and behind to confirm that all lights are illuminated and visible.

Clean the light lenses periodically with a soft cloth and mild soap. Road dirt, salt, and oxidation can dim the lights and make them harder to see from a distance. If a lens is cracked or the light is very dim, replace it before your next inspection.

During a roadside inspection by a Department of Transportation (DOT) officer, clearance lights are one of the first things checked. A burned-out or missing clearance light is a violation that can result in a citation and an out-of-service order until the light is repaired. Some jurisdictions allow a short grace period to fix the problem, but it is best not to rely on that.

Differences between clearance lights and other cab lights

Clearance lights are often confused with other marker lights on a truck, but they serve different purposes. Marker lights run along the sides and rear of the truck body and show the overall length and width of the vehicle. Identification lights are three amber lights mounted on top of the cab and are required on trucks over 80 inches wide. Side marker lights are smaller lights on the sides of the cab and cargo area.

Your truck may have all of these in addition to clearance lights, and each has its own wiring circuit and maintenance requirements. Clearance lights are specifically the ones at the top front corners and top rear corners of the cab itself, not the body or cargo area behind it.

What to do if a clearance light is not working

If you notice a clearance light is out, do not ignore it. Start by checking whether the bulb has burned out. Most clearance light bulbs are standard sizes (such as 194 or 168) that you can buy at any auto parts store for a few dollars. Turn off the truck, locate the light fixture, and replace the bulb following your owner's manual.

If the bulb is new but the light still does not work, the problem may be a blown fuse, a loose wire connection, or a failed socket. Check the fuse box (your manual will show you which fuse controls the clearance lights) and replace it if it is blown. If the fuse is good, the wiring or socket may need professional repair. Do not drive the truck on public roads with a non-functioning clearance light — have it repaired before your next trip.

If you are preparing for a DOT inspection or roadside check, test all your clearance lights the night before. This gives you time to address any problems before you are stopped by an officer.

Frequently Asked Questions

Do I need clearance lights if my truck is under 10,000 pounds GVWR?

No. Federal law requires clearance lights only on trucks with a GVWR over 10,000 pounds. If your truck is lighter than that, clearance lights are not mandated, though some states or local jurisdictions may have additional rules. Check your state's commercial vehicle regulations to be sure.

Can I use LED bulbs in my clearance lights?

Yes, LED bulbs are often a direct replacement for standard incandescent clearance light bulbs and use less power. Make sure the LED bulb is the correct size and brightness for your fixture and that it produces the correct color (amber for front, red for rear). Some older trucks may have wiring that does not work well with LEDs, so test them before relying on them for an inspection.

What happens if I get a citation for a burned-out clearance light?

A burned-out clearance light is typically a minor violation, but it can result in a fine and an out-of-service order until the light is repaired. The amount of the fine varies by state and jurisdiction. More importantly, it can delay your trip and affect your safety record if you are a commercial driver.

Do clearance lights stay on when the truck is parked?

No. Clearance lights are controlled by the ignition switch and turn off when you shut down the engine. If you need to mark your truck while it is parked (for example, on the roadside at night), you would use hazard lights or parking lights, not clearance lights.

Are clearance lights the same as identification lights?

No. Identification lights are three amber lights mounted on top of the cab and are required on trucks over 80 inches wide. Clearance lights are the corner lights that show the width and height of the cab. A truck may have both, and they are wired separately.