FMCSR 393.9T Inoperable Tail Lamp: Driver Q&A

Probably not, but it has happened. 393.9T is not automatically OOS-eligible, and the all-time OOS rate across our inspection records is 8.9%—well below the all-FMCSR average of 31.4%. Out of 14,785 all-time citations, 1,312 vehicles were still placed out of service, so inspectors do have discretion. The safest assumption is that a functioning tail lamp is required before you roll. Fix it before the next inspection and you stay in the 91.1% that drove away.

The severity weight for 393.9T is not published in our current data snapshot, so we can't give you a precise point value. What we can tell you is that 393.9T falls under the Vehicle Maintenance BASIC. Violations recorded within the last 6 months carry the heaviest time weight in the CSA SMS formula, and those in the last 12 months still count. With 8,814 citations recorded in just the last 12 months, inspectors are actively writing this one—meaning it will show up in your SMS record and affect your carrier's percentile.

Replace or repair the tail lamp before your next move if at all possible, then audit the rest of your lighting system immediately. Our inspection records show that in the last 90 days, 393.9T appeared alongside 393.9 (Inoperable Required Lamp) in 1,127 shared inspections and with 393.9TS (Inoperative turn signal) in 669 inspections—meaning inspectors who find one bad lamp almost always look for more. Also check: windshield condition (393.78, 419 shared inspections), emergency equipment (393.95A, 254 shared inspections), and your periodic inspection documentation (396.17C, 304 shared inspections). A single stop can produce multiple violations.

It's mid-tier on volume, lower-tier on OOS risk. Across our database, 393.9T ranks #174 out of 3,036 FMCSR codes by citation count—so it's enforced frequently. Its 8.9% OOS rate, however, is significantly below the all-FMCSR average of 31.4% and well below peer codes like 396.3(a)(1) at 45.3% OOS. The broader 393.9(a) lamp category has 660,737 citations at a 15.4% OOS rate, making 393.9T's rate look relatively contained. Serious enough to fix immediately; not in the same danger tier as brake or steering defects.

Yes, you can submit a DataQs Request for Data Review (RDR) for any 393.9T citation you believe was recorded in error. Because this is an equipment finding rather than a documentation violation, a successful challenge typically requires showing the lamp was in fact operable at the time of inspection—photos with timestamps, repair records dated before the inspection, or driver vehicle inspection reports (DVIRs) can all support your case. If the inspector entered the wrong code or the wrong vehicle, that is also challengeable. A decision in your favor removes the violation from your SMS record.

Texas by a wide margin, followed by Iowa and North Carolina. In the last 180 days our inspection records show Texas issued 3,156 citations, Iowa issued 462, and North Carolina issued 149. North Carolina stands out despite lower volume: its OOS rate for this violation is 38.3%, compared to Texas at 7.2% and Iowa at 10.2%. If you run lanes through North Carolina, inspectors there are far more likely to place a vehicle out of service for an inoperable tail lamp than inspectors in other top-citing states.

Don't wait. The data shows this is actively enforced: 1,980 citations in just the last 90 days, and monthly volume has stayed above 700 citations in most recent months. The 8.9% all-time OOS rate means roughly 1 in 11 drivers cited for this violation was parked on the spot. Inspectors are clearly not treating it as trivial. A tail lamp is also a fast, low-cost fix—there's no reasonable argument for deferring it to a scheduled PM when the exposure is this consistent.

Both. In the FMCSA CSA system, equipment violations like 393.9T are attributed to the carrier's Vehicle Maintenance BASIC, which affects the carrier's SMS percentile and can trigger interventions. The violation is recorded against the vehicle's inspections and tied to the carrier through the USDOT number. For the driver, the inspection appears on your PSP (Pre-Employment Screening Program) record, which prospective carriers can review when you apply for a job. Our all-time data shows carriers like Swift Transportation (26 citations) and Evans Delivery (26 citations) have accumulated meaningful 393.9T histories—fleet-level accumulation is real and visible.