Glossary
Power units
Power units are the vehicles with engines: straight trucks and truck tractors. Trailers are counted separately and are not power units. When the federal record says a carrier "has 12 trucks", it is reporting the power-unit count from the carrier's most recent MCS-150 filing.
Self-reported, and it matters
The power-unit count is what the carrier says about itself, refiled at least every two years. It is also the denominator behind the rates that make carriers comparable: crashes per 100 power units, expected inspection volume for a fleet that size, and the peer groups used for benchmarking. A wrong fleet size quietly distorts every one of those.
Claimed vs observed
The roadside record is the reality check. Each inspection names the actual vehicles inspected, so over time the public data shows how many distinct trucks have been seen on the road for a carrier. A claimed fleet with no inspection trail at all is itself a signal, and fleetfax surfaces it rather than treating the self-reported number as ground truth.
Related terms
MCS-150 (biennial update)
The registration form every carrier must refile at least every two years: fleet size, mileage, contact details. The freshness stamp on the federal record.
Roadside inspection (levels 1 to 6)
An enforcement officer's examination of a truck, its driver, or both, at weigh stations and roadside stops. The most abundant safety evidence in the public record; results feed OOS rates and CSA scoring.
USDOT number
The federal registration number every interstate carrier must hold. The primary key of the federal carrier record.
fleetfax reads public FMCSA data and is not affiliated with FMCSA or the U.S. Department of Transportation. This page explains terminology; it is not legal advice.