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A carrier's out-of-service (OOS) rate is the share of its roadside inspections that resulted in a vehicle or driver being placed out of service for a serious violation. It is one of the most direct, least-laggy safety signals available — derived straight from inspections, not a peer-relative percentile. This guide explains how the vehicle and driver OOS rates are calculated, how to compare them against the national averages, and how to read them as part of vetting a carrier.
A carrier's out-of-service rate is the percentage of its roadside inspections in which a vehicle or driver was placed out of service for a serious violation. It is calculated separately for vehicles and drivers: vehicle OOS rate is vehicle-OOS inspections divided by total vehicle inspections; driver OOS rate is the same for drivers. The rates are read against the national averages — vehicle OOS rates have historically hovered around one-fifth of inspections and driver OOS rates around one-twentieth, though the exact figures move year to year. A carrier well above the national average is a stronger present-tense risk signal than a lagging BASIC percentile.
When a roadside inspector finds a violation serious enough that continuing to operate would be an imminent hazard, they place the vehicle or the driver out of service — the truck cannot move, or the driver cannot drive, until the issue is corrected. A flat-out brake failure, a driver over their legal hours, a defective steering component: these are out-of-service conditions. A minor paperwork violation is recorded but does not put anyone out of service.
The out-of-service designation is therefore a severity filter built into the inspection itself. Every inspection produces a record; only the serious ones produce an out-of-service order at roadside. That makes the OOS rate a cleaner read on serious safety problems than a raw violation count, which mixes trivial and serious findings together.
A roadside out-of-service designation stops one truck or driver at one inspection. An out-of-service ORDER against a carrier's authority — covered in our separate guide — is an enforcement action prohibiting the whole carrier from operating. The OOS rate discussed here is about roadside inspections, not authority-level enforcement.
The out-of-service rate is a simple ratio, computed separately for vehicles and drivers over a rolling window of the carrier's inspections.
Because it is a straight ratio of inspections, the OOS rate is far less laggy than a peer-relative BASIC percentile. It moves as soon as new inspections land. Knowhaul computes both rates from the same inspection feed that powers the rest of the safety card, so the OOS rate and the underlying inspections stay in sync.
An OOS rate is only meaningful in comparison. Historically, the national vehicle out-of-service rate has run substantially higher than the driver rate — roughly on the order of one in five vehicle inspections producing an out-of-service condition, versus closer to one in twenty for drivers — but the exact national figures are published periodically and shift year to year, so treat those as orders of magnitude rather than fixed constants.
The read for a broker is relative position: a carrier whose vehicle OOS rate is well above the prevailing national average is failing roadside vehicle inspections more often than its peers, which points to maintenance problems. A high driver OOS rate points to hours-of-service or driver-qualification problems. A carrier comfortably below both national averages is demonstrating that its equipment and drivers pass inspection cleanly.
A vehicle out-of-service rate well above the national average is one of the clearest maintenance red flags. It means the carrier's trucks are repeatedly failing roadside inspection for serious mechanical defects — exactly the kind of carrier whose equipment is most likely to fail on your load.
Like any rate, the OOS rate is noisy when the denominator is small. A carrier with three inspections, one of which was an out-of-service, shows a 33% rate that tells you very little — one more clean inspection would cut it in half. A carrier with two hundred inspections and a stable rate is giving you a reliable signal.
Always read the OOS rate alongside the inspection count. A scary-looking rate on a tiny sample is a reason to read the individual inspections, not to draw a conclusion. A moderate rate on a large sample is a more trustworthy read than a perfect rate on a handful of inspections — the latter may just mean the carrier hasn't been inspected enough to surface its problems.
The OOS rate slots into the safety step of carrier vetting as the present-tense complement to the BASIC scores. Where a BASIC percentile is peer-relative and lagging, the OOS rate is absolute and fast-moving. The two together give a fuller picture: the BASIC tells you how the carrier ranks against peers; the OOS rate tells you how often its trucks and drivers are actually being pulled off the road.
A practical heuristic: a carrier below both national averages with a healthy inspection count is a low-risk read on safety; a carrier well above the vehicle average warrants a look at the maintenance-related inspections; a carrier well above the driver average warrants a look at the hours-of-service and driver-qualification record. Pair the rate with the raw inspections — covered in our roadside-inspections guide — to see exactly which violations are driving it.
A carrier comfortably below the national averages for both vehicle and driver out-of-service rates is a good read. Historically the vehicle rate has run on the order of one in five inspections and the driver rate closer to one in twenty, but the exact national figures shift year to year, so the meaningful comparison is relative position against the prevailing average rather than a fixed cutoff. A carrier well below both, with a healthy inspection count, is demonstrating clean equipment and compliant drivers.
They measure different things. The vehicle OOS rate reflects equipment condition — brakes, tires, lights, steering — placed out of service for serious mechanical defects. The driver OOS rate reflects driver compliance — hours-of-service violations, invalid licenses, missing medical certificates. A carrier can have a clean driver rate and a high vehicle rate (a maintenance problem) or the reverse (a driver-management problem), which is why the two are reported and read separately.
Neither is strictly better — they complement each other. The OOS rate is absolute and fast-moving, derived straight from inspections, so it's a strong present-tense signal. A BASIC percentile is peer-relative and lagging, so it tells you how the carrier ranks against similar carriers. The most reliable read uses both: the OOS rate for how often trucks and drivers are actually pulled off the road, the BASIC for relative standing. Reading them together beats relying on either alone.
It depends heavily on sample size and trend. A high rate on a small number of inspections may be statistical noise that one clean inspection would erase. A high rate that is trending down may reflect a carrier that has fixed a past problem. But a persistently high rate on a large inspection sample is a reliable signal of a real, ongoing safety problem. The right response to a high rate is to read the underlying inspections and the trend, not to accept or reject on the number alone.
Because it's computed directly from roadside inspections over a trailing window, the OOS rate updates as soon as new inspections land — much faster than a peer-relative BASIC percentile, which lags as bad inspections age out of its window. Knowhaul computes the rate from the same inspection feed that powers the rest of the safety card, so the OOS rate stays in sync with the underlying inspection history you can read alongside it.
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Roadside inspection records decoded for brokers — inspection levels, violation severity, OOS conditions, and how to read the inspection list as a near-real-time signal of carrier health.
CSA BASIC scores rank a carrier's safety against peers across seven behavior categories. Learn what each BASIC measures, how the percentile and intervention thresholds work, and how to read them when vetting a carrier.
The SAFER system explained — what the federal Safety and Fitness Electronic Records system actually returns, what 'safety rating' means versus BASIC scores, and how to read the numbers without misinterpreting them.
Step-by-step checklist for vetting any motor carrier before tendering a load — operating authority, insurance, safety scores, inspection history, and identity flags.
Open one of these profiles in a new tab to see how the checklist applies to a live carrier record.
Vehicle and driver out-of-service rates against the national average — with the underlying inspections one click away.