What 393.9B-LCL means in plain language
A clearance lamp is a light on the front upper corners and rear upper corners of your truck that marks its overall width and height to other drivers. The regulation requires these lamps to be visible and unobstructed—not covered by mud, ice, damage, or anything else that blocks the light from shining through.
When you get cited for 393.9B-LCL, the inspector found one or more of these lamps obscured. That could mean dirt caked on the lens, a cracked cover that's been taped over, condensation inside the fixture, or physical obstruction from cargo or equipment. The point is simple: if light can't pass through cleanly, it fails.
This is a maintenance issue, not a mechanical failure. You're not being cited because the lamp doesn't work—you're being cited because something is blocking its output.
What our enforcement data actually shows
Across our 13 million+ inspection records, 393.9B-LCL has generated 689 all-time citations, with 367 citations in the last 12 months and 79 in the last 90 days. That ranks it at #821 out of 3,036 FMCSR codes by citation volume—a relatively low-frequency violation.
The critical number: this code carries a 0.0% out-of-service rate. Of all 689 citations on record, not a single one resulted in the truck being placed out of service. Compare that to the all-FMCSR average of 31.4% OOS rate, and you'll see this violation is treated as a fix-it item, not a roadside shutdown.
The monthly trend over the last 12 months shows steady enforcement. Citation counts ranged from a low of 9 in April 2025 to highs of 40 in August 2025 and 39 in May 2025, averaging around 31 per month. This tells you inspectors are consistently catching obscured clearance lamps year-round.
Who gets cited most
California leads by far, with 41 citations in the last 180 days—more than double any other state. New York follows with 19 citations, and Florida with 11. All three states show a 0.0% OOS rate, confirming that even the most frequent states treat this as a non-critical defect.
Among vehicle makes, our data shows Freightliners account for 88 all-time citations for this code, followed by Frht (73 citations) and Ford (48 citations). This reflects the popularity of those models in commercial fleets rather than a specific vulnerability—any vehicle type can accumulate dirt on its clearance lamps.
How severe is this compared to similar codes
The most closely related code is 393.9A-LIL (Inoperable required lamps), which has generated 660,737 citations with a 15.4% OOS rate. That code addresses lamps that don't work at all; this code is about lamps that work but can't be seen. The difference in OOS rates (15.4% vs. 0.0%) shows inspectors and enforcement prioritize actual failures over visibility problems.
Another peer is 393.78 (Windshield condition defective), with 157,894 citations and a 0.3% OOS rate. Like your citation, visibility issues that don't render the vehicle unsafe are rarely grounds for shutdown. The code 396.3(a)(1) (Inspection/repair/maintenance—general) sits much higher at 45.3% OOS rate, showing that structural or safety-critical maintenance defects are treated far more severely.
How to avoid it
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Clean all four clearance lamps during your pre-trip inspection. Use a soft cloth and mild cleaner—water and soap work fine. Check the top corners of your cab and the top corners of your trailer. If you see condensation inside the lens, the seal is failing and the lamp will need replacement.
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Check clearance lamp condition after driving in wet, muddy, or dusty conditions. Mud splatters and dust accumulate fastest on these high-mounted lights. A quick roadside wipe-down can prevent a citation at the next inspection.
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Inspect the lens for cracks or cloudiness. A cracked lens may still light up, but it's partially obscured. If you see damage, request a replacement before your next heavy-traffic area or scale.
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Keep cargo secured away from the rear corners. Improperly secured loads can shift and cover rear clearance lamps during transit. Use proper blocking and bracing to maintain visibility around all four lamps.
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Pair clearance lamp checks with your general lighting inspection. Our data shows 393.9A-LIL (Inoperable required lamps) and 393.9B-LIL (Identification lamp obscured) often appear in the same inspection as your code. Check all lamps—headlights, taillights, turn signals, and clearance lamps—in one pass.
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Don't rely on darkness to hide defects. Inspectors use flashlights and check visibility in daylight. What looks okay at night under your lights will be obvious to an inspector during the day.