FMCSR 390.21(b): USDOT Number Not Displayed — Driver FAQ

No. Across all 13,244 citations for 390.21(b) in our inspection records, only 1 vehicle was ever placed out of service — giving this code a 0.0% OOS rate. For context, the average OOS rate across all FMCSR codes is 31.4%, so 390.21(b) sits far below the norm. You will almost certainly be allowed to keep moving after receiving this citation. That said, the violation still goes on your inspection record and feeds into CSA scores, so it is not something to ignore entirely.

390.21(b) carries a CSA severity weight of 3. That is the base point value assigned to this violation. FMCSA's SMS system applies a time-weight multiplier on top of that: violations within the last 6 months are multiplied by 3, violations from 6–12 months ago by 2, and violations older than 12 months by 1. So a fresh 390.21(b) citation effectively counts as 9 weighted points in your Unsafe Driving or Vehicle Maintenance BASIC until it ages out. The violation falls under the General/Admin group, which maps to the Vehicle Maintenance BASIC in CSA scoring.

Fix the marking and audit the rest of the vehicle immediately. Our inspection records show that in the last 90 days, 390.21(b) appeared alongside 396.17C (no proof of periodic inspection) in 54 shared inspections, and with 392.2FT (operating while fatigued) in 50. That pattern means inspectors who catch a missing USDOT number keep looking. Concrete steps:

1. Confirm your USDOT number is displayed on both sides of the CMV in the required size and color.
2. Pull your periodic inspection documentation (396.17C was the top co-occurring code).
3. Check all required lamps and turn signals — 393.9TS and 393.9 each appeared in 37 and 24 shared inspections respectively.
4. Verify your fire extinguisher is present and serviceable (393.95A, 31 shared inspections).
5. Keep a copy of the citation for DataQs if the marking was actually present and was missed.

It is a mid-volume admin violation with essentially zero equipment risk. At 13,244 all-time citations, 390.21(b) ranks #185 out of 3,036 FMCSR codes by citation volume — active enough to matter for CSA, but not a top-tier enforcement priority. Its 0.0% OOS rate matches most of its peer codes in the same category: 390.21TB2-DOT (74,663 citations, 0.0% OOS), 390.21(a) (25,872 citations, 0.0% OOS), and 390.19B2-BIENNIAL (16,142 citations, 0.2% OOS) all sit at or near zero. The national FMCSR average of 31.4% OOS makes clear this is a paperwork/marking issue, not a safety-critical defect.

Yes, and this type of violation is often worth contesting if the USDOT number was actually present. Because 390.21(b) is a marking/documentation finding rather than a mechanical defect, a DataQs Request for Data Review (RDR) can be effective. If you have photos, GPS records, or other evidence showing the number was properly displayed at the time of inspection, submit them through FMCSA's DataQs portal. The RDR goes to the issuing state agency for review. Given that this code has a 0.0% OOS rate and 13,243 out of 13,244 inspections resulted in no OOS action, disputes that are well-documented tend to be straightforward to evaluate.

North Carolina and New Mexico dominate enforcement of this code. In the last 180 days, NC issued 439 citations for 390.21(b) with a 0.0% OOS rate, and NM issued 152 citations, also at 0.0% OOS. Pennsylvania appears in the top-state list as well with 1 citation in the same window. If your routes regularly pass through North Carolina or New Mexico, verifying your USDOT markings before entry is a simple, low-cost step that the data strongly supports.

Moderately urgent — volume has been consistently elevated and is not declining. Our inspection records show 1,536 citations issued in the last 12 months alone, and 247 in just the last 90 days. Monthly counts have held in the 100–166 range from October 2025 through January 2026. The 0.0% OOS rate means you won't be parked, but repeated citations accumulate CSA points rapidly under the time-weight multiplier. A carrier sitting at a severity weight of 3 per hit, multiplied by 3 for recency, can see BASIC scores move quickly if the marking issue goes uncorrected across a fleet.

Both, but the carrier bears the heavier burden. FMCSA's CSA system attributes vehicle marking violations like 390.21(b) to the carrier's Vehicle Maintenance BASIC, since proper USDOT display is a carrier responsibility under the regulations. The driver's safety record also reflects the inspection event. Our records show that fleet-level exposure is real: HOME EXPRESS DELIVERY SERVICE LLC accumulated 20 all-time citations, CTC CORPORATION LLC had 17, and IMAGE FIRST HEALTHCARE LAUNDRY SPECIALISTS LLC had 14 — demonstrating that when carriers don't enforce marking standards across their vehicles, the citations stack up in ways that affect BASIC percentiles.