The DOT (or USDOT) is a federal Cabinet department of the U.S.
government concerned with transportation. It was established in 1966
and began operating on April 1, 1967. It is governed by the United
States Secretary of Transportation.
Its mission is: "To serve the United States by ensuring a fast, safe,
efficient, accessible, and convenient transportation system that meets
our vital national interests and enhances the quality of life of the
American people, today and into the future."
To achieve its mission it legislates regulations for CMVs requiring them
to register for a USDOT number. Regulations for CMVs include HOS and
DVIRs. If a roadside inspections by DOT officers (or State Troopers) or
DOT audit uncovers non-compliance this can hurt a fleet's CSA score.
CMV operators often use compliance software to automate their processes
to make sure their drivers and vehicles are compliant at all times.