FMCSR 393.9(a) Inoperable Required Lamps: Driver Q&A

Most of the time, no—but it has happened. Across all-time inspection records for 393.9(a), 15.4% of citations resulted in an out-of-service order, meaning roughly 1 in 6.5 drivers were pulled. That's actually well below the all-FMCSR average OOS rate of 31.4%, so inspectors treat most inoperable lamp violations as serious but not automatically grounds to park you. That said, 101,445 drivers in our database were placed out of service under this code, so the risk isn't zero. Severity of the defect and the inspector's judgment on overall vehicle condition play a role in that call.

A citation under 393.9(a) carries a CSA severity weight of 3. That base score is then multiplied based on how recently the inspection occurred—violations in the last 6 months carry the highest weight in FMCSA's SMS calculation, with the multiplier stepping down at the 6-month and 12-month marks. The points land in the Vehicle Maintenance BASIC (BASIC 5). Both the driver's PSP record and the carrier's SMS profile are affected. With 660,737 all-time citations, this is the second most-cited FMCSR code out of 3,036, which signals inspectors are actively watching for it.

Act the same day. Here's the short list:

1. Identify every inoperable lamp on the unit—don't just fix the one the inspector flagged.
2. Make the repair before your next dispatch. The OOS rate for this code is 15.4%, and a second encounter with a non-fixed lamp could result in being parked.
3. Document the repair with a work order or mechanic sign-off. Date and mileage matter if you ever file a DataQs challenge.
4. Notify your fleet safety manager or carrier. The citation hits the carrier's BASIC score too, so they need to know and may have a corrective action process to follow.
5. Check your co-occurring exposure—lamp violations often appear alongside other equipment defects during the same inspection.

It's serious by volume, less so by OOS rate. At 660,737 all-time citations, 393.9(a) ranks #2 out of 3,036 FMCSR codes—that's not a minor footnote violation. However, its 15.4% OOS rate is considerably lower than the all-FMCSR average of 31.4%, and lower than the peer code 396.3(a)(1) (general inspection/repair/maintenance), which carries a 45.3% OOS rate. The related code 393.9 (without the subsection) shows a 6.9% OOS rate across 180,097 citations. So while inspectors cite 393.9(a) constantly, they park drivers for it at a below-average rate compared to the broader universe of FMCSR violations.

Yes, you can submit a DataQs Request for Data Review (RDR) to challenge the citation. Because 393.9(a) is an equipment-condition finding rather than a documentation violation, a successful challenge typically requires evidence that the lamp was actually operational at the time of inspection—repair records dated before the inspection, photos with timestamps, or a prior inspection report showing the lamp was functional. DataQs challenges on equipment findings have a higher bar than documentation disputes; you're arguing the inspector's observation was incorrect, not just that paperwork was misfiled. If the record is corrected, it's removed from both your PSP and the carrier's SMS BASIC calculation.

The top carriers in our inspection database for 393.9(a) citations include operations with major national footprints, but the records don't isolate citation counts by state for this code in the current data snapshot. What the data does confirm is that the code has accumulated 660,737 all-time citations nationally, making it the second most-cited code across all 3,036 FMCSR rules. The carriers with the highest citation counts—EVANS DELIVERY COMPANY INC (1,393 citations), J B HUNT TRANSPORT INC (1,305 citations), and SWIFT TRANSPORTATION CO OF ARIZONA LLC (1,077 citations)—operate heavily across high-inspection-volume corridors, suggesting enforcement is concentrated along major freight lanes rather than limited to any single region.

Don't wait. The inspection record for 393.9(a) shows 0 citations in the last 90 days and 0 in the last 12 months in the current snapshot, which reflects a data cutoff issue rather than enforcement going away—this code has 660,737 all-time citations and ranks #2 nationally, so it remains a heavily enforced area. More importantly, 15.4% of all citations for this code resulted in an out-of-service order. If you're cited again with the same lamp still inoperable, the inspector has clear grounds to park the vehicle. Fix it before the next run, document the repair, and don't let a $3 bulb become a CSA severity-3 hit on your record.

Both are affected, but in different ways. The citation appears on the driver's PSP (Pre-Employment Screening Program) record, where prospective employers can see it. It simultaneously counts against the carrier's Vehicle Maintenance BASIC score in FMCSA's Safety Measurement System. The carrier absorbs the SMS impact because equipment condition is considered a carrier responsibility under FMCSR—the carrier is expected to ensure vehicles are roadworthy before dispatch. With a CSA severity weight of 3 and 393.9(a) ranking #2 out of 3,036 codes by citation volume, fleets accumulating this violation across multiple units will see measurable BASIC score deterioration over the 24-month SMS rolling window.