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The most common DOT violations are vehicle defects, not driver paperwork. In FMCSA's roadside data for September 25, 2025 to September 24, 2026, the most-cited violations were flat or badly underinflated tires, brakes out of adjustment, no proof of a periodic inspection, and inoperable lamps. Vehicle Maintenance violations made up 74.5% of the 3.54 million violations recorded.
The eight violations this guide covers, in order of how often FMCSA's data shows them:
- Flat, leaking or badly underinflated tires
- Brakes out of adjustment
- No proof of a periodic (annual) inspection
- Inoperable required lamps, including identification and clearance lamps
- Failing to obey a traffic control device, and speeding
- Trailer ABS malfunction lamp defects and automatic slack adjusters that fail to compensate
- No valid medical certificate
- English language proficiency
Each one is tied to a rule in the Federal Motor Carrier Safety Regulations. All regulation references below are to the eCFR text current as of October 2026, and every rule cited is a final rule in effect unless we say otherwise.
Where these numbers come from
The ranking above is our count of FMCSA's own published file, the SMS Input - Violation dataset on data.transportation.gov. FMCSA describes it as the publicly available violation data used for the current month's Safety Measurement System (SMS) calculations, one violation per row. The copy we counted was updated October 13, 2026.
How we counted:
- The file covers 24 months. We kept the 12 most recent, using FMCSA's own time-weight field (weights 3 and 2 cover the latest 12 months; in this file that is September 25, 2025 to September 24, 2026).
- That leaves 3,539,342 violations on 1,390,268 inspections that had at least one violation in the file.
- 838,475 of those violations were marked out of service (OOS).
- We counted FMCSA's violation codes as written. One inspection can carry several violations, so these are violation counts, not inspection counts.
FMCSA uses roadside violations in SMS even when no ticket is written, which is why this file matters to your BASIC percentiles. If you want the background on how those percentiles work, see our guide to CSA BASICs.
Violations by BASIC, last 12 months
| BASIC | Violations | Share |
|---|---|---|
| Vehicle Maintenance | 2,637,978 | 74.5% |
| Unsafe Driving | 327,676 | 9.3% |
| Hours-of-Service Compliance | 320,754 | 9.1% |
| Driver Fitness | 225,475 | 6.4% |
| Hazardous Materials Compliance | 20,174 | 0.6% |
| Controlled Substances/Alcohol | 7,285 | 0.2% |
Source: FMCSA SMS Input - Violation file, inspections dated Sept. 25, 2025 to Sept. 24, 2026, counted October 20, 2026.
The 15 most-cited violation codes
| Rank | FMCSA violation description (shortened) | CFR | Count |
|---|---|---|---|
| 1 | Tire flat, leaking, or under 50% of max inflation (no ATIS) | 393.75(a)(3) | 94,725 |
| 2 | Brake out of adjustment (clamp, roto, DD-3 or bolt type) | 393.47(e) | 87,176 |
| 3 | Operating a CMV without proof of a periodic inspection | 396.17(c) | 81,859 |
| 4 | Inoperable required lamp | 393.9 | 77,608 |
| 5 | Failed to obey a traffic control device (state/local law) | 392.2 | 59,740 |
| 6 | Identification lamp(s) inoperative | 393.9 | 59,170 |
| 7 | ABS malfunction lamp defective on trailers built on or after March 1, 1998 | 393.55 | 55,043 |
| 8 | No valid medical certificate (property carrier) | 391.41 | 52,932 |
| 9 | English language proficiency (FMCSA's border-zone code; almost never OOS) | 391.11(b)(2) | 51,858 |
| 10 | Automatic brake adjuster fails to compensate for wear | 393.53(b) | 51,458 |
| 11 | Speeding 6 to 10 mph over the limit (state/local law) | 392.2 | 48,926 |
| 12 | Audible air leak at a proper connection | 393.45 | 47,102 |
| 13 | Inoperative windshield washing system | 393.78 | 47,021 |
| 14 | Stopped-vehicle warning devices missing or improper | 393.95(f) | 45,296 |
| 15 | Air hose or tubing damaged or not secured | 393.45 | 43,860 |
Grouped the way FMCSA groups them, brakes lead: the "Brakes All Others", "Brakes Out of Adjustment" and "Brake Out of Service" groups together hold 755,989 violations. Lighting and clearance or identification lamps together hold 604,469.
What inspectors put trucks and drivers out of service for
A violation on its own counts in your SMS measures. An out-of-service order also costs you the load. The most frequent OOS violations in the same 12 months:
| Rank | OOS violation (FMCSA description, shortened) | OOS count |
|---|---|---|
| 1 | Tire flat, leaking, or under 50% of max inflation | 94,472 |
| 2 | No valid medical certificate (property carrier) | 52,168 |
| 3 | Defective brakes equal to or over 20% of service brakes | 41,919 |
| 4 | No record of duty status in the method prescribed | 33,974 |
| 5 | Rear turn signal inoperative | 30,733 |
| 6 | No valid CDL | 29,789 |
| 7 | Both stop lamps inoperative | 24,062 |
| 8 | English language proficiency (OOS version of the code) | 21,441 |
CVSA's three-day check points the same way. In the 2026 International Roadcheck results (released August 25, 2026), the top vehicle OOS categories in the U.S. were brake systems (2,816, 23.6%), tires (2,669, 22.3%), 20% defective brakes (1,846, 15.4%), lights (1,514, 12.7%) and cargo securement (1,438, 12.0%). The top U.S. driver OOS violations were no medical card (1,072, 28.2%), hours of service (883, 23.2%), no CDL (614, 16.1%), English proficiency (361, 9.5%) and false records of duty status (214, 5.6%).
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The eight most common DOT violations and how to prevent each
1. Flat, leaking or underinflated tires (393.75)
Under 49 CFR 393.75, no vehicle may run on a tire that is flat or has an audible leak, has exposed ply or belt, or has tread or sidewall separation. Steer tires need at least 4/32 inch of tread and other tires at least 2/32 inch. This was the single most-cited violation and the most frequent OOS violation in the file. Prevention: a gauge check, not a thump, on the pre-trip; a written inflation target per tire size; and a rule that a tire found under target is fixed before dispatch, not at the next shop visit.
2. Brakes out of adjustment (393.47 and 393.53)
49 CFR 393.47(e) sets the maximum pushrod stroke for each brake chamber type and size. Out-of-adjustment brakes ranked second, and automatic adjusters that fail to compensate for wear ranked tenth. An automatic slack adjuster that keeps needing manual adjustment is a failing part, not a maintenance task. Prevention: measure stroke at each PM, replace adjusters that drift instead of re-adjusting them, and train drivers on the walk-around signs.
3. No proof of a periodic inspection (396.17)
49 CFR 396.17(c) bars using a vehicle unless every unit passed an inspection in the preceding 12 months and documentation is on the vehicle. That includes each trailer and converter dolly. Nearly 82,000 citations make this the most avoidable entry on the list. Prevention: a due-date list for every unit, trailers included, and a decal or report check on every pre-trip.
4. Inoperable lamps (393.9)
49 CFR 393.9(a) requires every required lamp to be capable of operating at all times. Inoperable required lamps, identification lamps and clearance lamps all sit in the top 25 codes, and a dead rear turn signal or both stop lamps out is an OOS condition. Prevention: a lights check on every pre-trip and every fuel stop, and spare bulbs and fuses in the truck.
5. Traffic control devices and speeding (392.2)
These are Unsafe Driving violations cited under state and local law through 49 CFR 392.2. Failing to obey a traffic control device ranked fifth. Speeding 6 to 10 mph over was 48,926 citations, 11 to 14 mph over was 26,958, and 15 mph or more over was 18,155. CVSA's Operation Safe Driver Week 2026 (July 12–18) again found speeding the most-cited unsafe driving behavior. Prevention starts with dispatch: a schedule that can only be met by speeding produces speeding. Our accident-prevention guide covers taking speed out of the schedule.
6. Trailer ABS lamps and other brake components
Defective ABS malfunction lamps on trailers built on or after March 1, 1998 drew 55,043 citations. Audible air leaks (47,102) and damaged or loose air hoses (43,860) follow close behind. These are cheap fixes that inspectors can see from the shoulder. Prevention: check the trailer ABS lamp at hookup, and put air-line condition on every trailer PM.
7. No valid medical certificate (391.41)
49 CFR 391.41(a) says a driver must not operate a CMV unless medically certified. Since June 23, 2025, a CDL or CLP holder with a current certificate no longer has to carry the paper card, per 391.41(a)(2)(i)(B). The violation is still the second most frequent OOS order in the file. Prevention: track every driver's certificate expiration date and confirm the state record shows it as current, well before the date.
8. English language proficiency (391.11(b)(2))
Counting all four violation codes FMCSA uses for it, English language proficiency was cited 76,798 times in the 12 months. About 24,300 of those were OOS. As of October 2026, FMCSA has a proposed rule (91 FR 51422, August 10, 2026) to codify English proficiency as an out-of-service violation. Its comment period closed October 9, 2026, and it is not final. Prevention: assess English proficiency at hiring and in road tests, against the 391.11(b)(2) standard.
Hours-of-service and driver violations worth watching
Hours-of-service violations were 9.1% of the total, but several of them carry heavy SMS weight. Six codes worth watching, with their counts in the file:
- No record of duty status in the method prescribed (395.8(a)): 35,774
- False report of duty status (395.8(e)): 32,773
- Driver failing to review and certify ELD records: 19,211
- Driving past the 14-hour window: 9,267
- Driving more than 11 hours: 8,733
- Improper personal conveyance logged as off duty: 7,004
For the limits behind those codes, see our hours of service rules guide. The three driver seat belt codes (392.16) added another 40,554 citations, and the two driver hand-held phone codes (392.82) 8,923.
A prevention checklist by violation
| Violation | Rule | Check | When |
|---|---|---|---|
| Tires | 393.75 | Gauge every tire; tread 4/32 steer, 2/32 others | Every pre-trip |
| Brake adjustment | 393.47(e), 393.53(b) | Measure stroke; replace drifting adjusters | Every PM |
| Periodic inspection | 396.17(c) | Proof on every unit, trailers included | Every pre-trip; due list monthly |
| Lamps | 393.9 | All required lamps, ID and clearance lamps | Pre-trip and fuel stops |
| Trailer ABS lamp | 393.55 | Lamp check at hookup | Every hookup |
| Emergency equipment | 393.95 | Rated, charged, secured extinguisher; three triangles | Every pre-trip |
| Medical certificate | 391.41 | Expiration date tracked; state record current | 60 days before expiry |
| Hours of service | 395.8 | Logs certified; no edits that hide limits | Daily review |
What to do after a violation
Every violation on an inspection report feeds SMS for 24 months, weighted toward the most recent. If a violation was recorded in error, you can ask for a review through DataQs; our guide to challenging a violation in DataQs walks through it. If it was correct, the fix is upstream. Find the process that let the defect leave the yard. Our guide on how to improve your CSA score covers that work in order.
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This article is general information, not legal advice. Confirm requirements against the current regulation text and with your compliance counsel.
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