Are Your Clearance Lights DOT-Compliant?
Clearance lights might be small, but when they’re non-compliant, they create outsized problems — failed inspections, CSA score hits, citations, and worse, unsafe driving conditions. Because they're often overlooked during routine inspections, it's important for technicians and shop managers to understand exactly what the DOT expects.
Making sure your DOT trailer clearance lights are compliant isn’t just about flipping a switch and checking for glow — it’s about placement, color, function, and circuit integrity.
What Are Clearance Lights — and Why Do They Matter?
Clearance lights are federally required indicators mounted on the front and rear upper corners of trailers. Their primary function is to outline the extreme width and height of the vehicle, especially in low-visibility conditions like night driving, fog, or heavy rain.
These lights:
Help other drivers gauge the size of the trailer
Reduce the chance of side-swipe or clearance-related accidents
Serve as visual references when backing into tight spaces
Contribute to overall FMVSS 108 lighting compliance
Missing, damaged, dim, or improperly placed clearance lights are among the most common trailer lighting violations cited during DOT inspections.
DOT Clearance Light Requirements for Trailers
According to FMVSS 108 and DOT regulations, here’s what’s required for trailer clearance lights:
Front clearance lights must be amber and located on the upper corners of the front
Rear clearance lights must be red and located on the upper corners of the rear
Lights must be visible from a specific distance (typically 500 feet)
Lights must be functional whenever the vehicle’s lights are on
Circuit and ground integrity must support consistent brightness
Improper color or placement alone is enough to trigger a compliance violation — even if the light is working.
Common Issues That Lead to Violations
Technicians might perform visual checks, but not all faults are easy to see. Common clearance light violations include:
Cracked or discolored lenses
Dim operation due to voltage drop
Incorrect color (e.g., red up front or amber in back)
Loose mounting or misplacement
Open circuits or high-resistance grounds
Flickering due to corrosion or pin damage
These faults can go unnoticed until an inspector spots them — or a driver reports being pulled over.
How to Inspect Clearance Lights Properly
A full inspection of DOT trailer clearance lights should include more than a basic visual once-over. Best practices include:
Verifying proper lens color and brightness at night or in low light
Checking voltage at each light with a diagnostic tool
Ensuring ground paths are secure and free from corrosion
Testing lights under full system load to catch flicker or dimming
Confirming all upper-corner locations are covered and lights are operational
Remember, it only takes one non-compliant clearance light to result in a violation.
Equip Your Shop to Catch Every Lighting Violation
Manual light checks can miss subtle but costly problems. The Inspector 930 gives your shop the capability to:
Simulate power to every trailer circuit without the truck
Verify voltage across every lighting function — including clearance lights
Detect open circuits, weak grounds, and shorts
Run a one-person, full-system lighting diagnostic in minutes
Built for shop floors and mobile service units, the Stryker 1000 ensures lighting inspections aren’t just checked off — they’re completed with confidence.
Don’t Let Clearance Lights Be a Compliance Gap
Clearance light violations are easy to miss — but costly when found. When you use the right DOT trailer clearance lights and test them with precision, you reduce inspection risks and improve fleet safety across the board.
To integrate lighting diagnostics into your PM program, visit Lite-Check.com, call 509-535-7512, or email info@lite-check.com.