Methodology & data sources

Sources

• NHTSA vPIC — VIN decoding: make, model, year, body class, GVWR, engine.
• FMCSA Inspection files — roadside inspection records.
• FMCSA Inspections Per Unit — VIN, unit number, plate state, carrier/USDOT association.
• FMCSA Violations — violation codes, descriptions, OOS status, unit-level attribution.
• FMCSA Company Census — carrier legal name, DBA, USDOT number.

Unit-specific violation attribution

A single roadside inspection can include multiple units — for example a tractor and a trailer. Violations are recorded per unit. We attribute a violation to the searched VIN only when the violation's inspection ID and unit number match a unit that the VIN actually occupied. We never assign a trailer's defect to the tractor, or vice versa.

VIN matching

• VINs are normalized to uppercase with spaces and punctuation removed.
• Only exact 17-character VINs are accepted; I, O, and Q are rejected.
• We use exact VIN matches only — no fuzzy matching, and we never silently correct a VIN.