USDOT refers to the US Department of Transportation, the federal agency responsible for the country’s transportation system and its regulation. The FMCSA, which governs trucking safety, sits within it.
In everyday trucking, “USDOT number” is the unique ID assigned to a commercial carrier, used to track its safety record, inspections, and compliance. Paired with the MC Number, it identifies a carrier across federal systems and appears on the truck and its registration paperwork.