Commercial Truck VIN & DOT Glossary
Plain-English definitions for the terms used in commercial truck VIN decoding and DOT roadside inspection history.
Last updated: June 2026 · Data sources: NHTSA vPIC (live) and FMCSA public inspection records (periodic refresh).
- VIN
- Vehicle Identification Number — a unique 17-character code identifying a specific vehicle.
- WMI
- World Manufacturer Identifier — the first three VIN characters identifying country, manufacturer, and vehicle type.
- VDS
- Vehicle Descriptor Section — VIN positions 4–8 encoding model, body, engine, GVWR, and brakes.
- Check digit
- VIN position 9 — a calculated value used to validate the VIN against transcription errors.
- GVWR
- Gross Vehicle Weight Rating — the maximum loaded weight. Class 3–8 (over 10,000 lb) is generally commercial/heavy-duty.
- Truck-tractor
- The power unit that pulls a semi-trailer; the 'tractor' in a tractor-trailer combination.
- NHTSA vPIC
- The National Highway Traffic Safety Administration's VIN decoder, used to decode VIN specs.
- FMCSA
- Federal Motor Carrier Safety Administration — the agency whose public data includes roadside inspections and violations.
- SAFER
- FMCSA's Safety and Fitness Electronic Records system, including the Company Snapshot.
- USDOT number
- A unique identifier FMCSA assigns to a motor carrier.
- Roadside inspection
- An enforcement check of a commercial vehicle and driver, usually performed roadside under FMCSA's program.
- Inspection level
- The scope of a roadside inspection (I–VI). Level I is the most thorough vehicle-and-driver inspection.
- Out-of-service (OOS)
- A serious condition found in an inspection that stops the driver or vehicle until corrected.
- Violation code
- The regulatory code (e.g., 49 CFR §393.x) identifying a specific cited condition.
- Unit number
- Identifies which unit (e.g., tractor vs trailer) a violation belongs to within an inspection.
- Unit-specific attribution
- Assigning a violation to the exact unit a VIN occupied — so a trailer's defect is not blamed on the tractor.
- Carrier observed operating a VIN
- A carrier that appeared with a VIN in roadside records — context, not legal ownership.
- NMVTIS
- National Motor Vehicle Title Information System — the source for title, brand, and odometer history via approved providers.
- Title brand
- A designation on a title (e.g., salvage, rebuilt) — not part of FMCSA data; check an NMVTIS provider.