A USDOT Number stands for U.S. Department of Transportation number. A USDOT# is a way for the government to track carriers on their system. A carrier that has a truck that is over 10,000 lbs is required to have this number in place. The USDOT number is assigned to a census record in the Motor Carrier Management Information System (MCMIS). Each motor carrier should have only one active number. Numbers are issued sequentially as carriers are added to the system.