Sort any roadside violation table by count and you get a list full of bulbs, wipers, and fire extinguishers. Sort the same table by out-of-service rate and it looks like a different industry. I pulled both views from the VioCodes dataset, and the gap between them is the most useful thing in it.
Before you quote any of these figures, check the date range behind them on the insights page. I'm giving the counts as the dataset holds them and not restating a window here, so don't carry these numbers into a report without that context.
Start with the six BASICs
Vehicle Maintenance is the largest category by a wide margin: 15,233,046 violations, with 3,303,635 of them out of service. By my arithmetic that is about 21.7%. Hours-of-Service Compliance logged 2,223,914 violations and 476,873 out of service, roughly 21.4%.
Driver Fitness behaves differently. It logged 1,104,639 violations, and 662,839 were out of service, about 60%. Controlled Substances/Alcohol is small at 52,899 violations, but 51,517 were out of service, close to 97%. Hazardous Materials Compliance logged 160,441 violations with 46,271 out of service, around 29%.
Unsafe Driving logged 1,713,588 violations and only 336 out of service. I won't read that as "unsafe driving is safe." The dataset doesn't say why those violations so rarely end in an out-of-service order, and I'd rather not guess in print. What it does show is that a high count and a high out-of-service rate are separate questions.
The most-cited codes are mostly cheap fixes
The top code by count is 393.9, Inoperable Required Lamp, at 1,141,810 violations. In our dataset it carries a severity weight of 2. Behind it come:
- 393.47(e), Brake Out of Adjustment: 617,809 (weight 4)
- 396.17(c), operating a CMV without proof of a periodic inspection: 588,710 (weight 4)
- 396.17C-PI, operating a CMV without documentation of a periodic inspection: 417,837 (weight 4)
- 393.95(a), no/discharged/unsecured fire extinguisher: 374,204 (weight 2)
- 393.9TS, inoperative turn signal: 352,784 (weight 6)
- 393.75(a)(3), tire flat and/or audible air leak: 325,795 (weight 8)
- 393.78, wipers: 317,726 (weight 1)
Two of these deserve to be read together. 396.17(c) and 396.17C-PI describe the same basic gap in plain language: the truck cannot show a current periodic inspection. The dataset keeps them as separate codes, so counted separately they are 588,710 and 417,837. Combined, that is 1,006,547 violations for one paperwork problem. If you are deciding where to put compliance effort, treat them as one problem.
Note also that a brake code, 393.47(e), sits near the top of the count list at weight 4. Frequency and consequence are different things, and the next section is where that difference shows up.
Where the out-of-service rate points
The top code by out-of-service rate is 396.3A1BOS, a brake defect equal to or greater than 20% of the service brakes on the vehicle or combination. It was written 278,496 times and resulted in 277,706 out-of-service violations, a 99.7% rate. In our dataset its severity weight is 0. That is the point of this whole post: a weight field on its own can understate what happens at the roadside. Read it alongside the out-of-service column before you rank anything.
Brakes dominate this list. Four of the ten highest-rate codes are brake codes:
- 396.3A1BOS, 99.7%
- 393.43DBMA, breakaway not attached to the towing vehicle, 99.1%
- 393.41-BNPB, inoperative or missing parking brake on the power unit, 98.8%
- 393.43D-B, missing or inoperable breakaway braking system on a trailer or converter dolly, 98.3%
Lighting shows up too. 393.9A-LSLIWR, both stop lamps inoperative when required to be on, is out of service 99.0% of the time (63,983 of 64,622). Compare that with 393.9 at 1,141,810 violations. Both are lamp codes. The general one is a common ticket; the stop-lamp one is almost always a truck parked.
Two CDL codes also sit in the top ten. 383.23(a)(2), operating a CMV without a CDL, is out of service 98.9% of the time (171,942 of 173,894), and 383.23A2-LCDLN, operating without a valid CDL, runs at 98.7%. Tires (393.75G-TAOW at 98.7%, 393.75A3-TAOLTIS at 98.2%) and cargo securement (393.100B-C at 98.5%) round out the list.
What to take from it
Key takeaways
- Count tells you what you will see at the roadside. Out-of-service rate tells you what ends the trip. The two overlap less than most fleets assume.
- Lamp, wiper, and extinguisher codes dominate the count list. Keep them fixed, because they are written constantly, but don't mistake frequency for consequence.
- Brake codes dominate the out-of-service list. 396.3A1BOS is out of service 99.7% of the time even though its severity weight is 0 in our dataset.
- Vehicle Maintenance is the largest BASIC on both counts and out-of-service violations, with 3,303,635 out of service. Most of the volume sits there.
- Don't rank priorities on severity weight alone.
The limits of this view
The dataset records what inspectors wrote. It does not measure crash risk, and it does not explain why a given code has the rate it does. An out-of-service rate describes how a violation gets handled at roadside. It is not a direct measure of danger. Counts are also violations, not trucks, so one truck with three findings adds three to the totals.
When you need the exact wording of a code on this list, start with the violations index, then confirm the requirement against the regulation text on eCFR before you act on it.