Federal Motor Carrier Safety Administration (FMCSA)
The federal agency regulating commercial motor vehicle safety. Its rules govern driver qualification, inspection and maintenance for regulated vehicles.
FMCSA sets and enforces the safety rules for commercial motor vehicles: who may drive them, how they must be inspected and maintained, and what records are kept.
Public fleets sit in a mixed position. A jurisdiction may hold a DOT number and operate regulated vehicles alongside a much larger population of unregulated light-duty ones, so the same fleet runs two compliance realities at once. Knowing which of your vehicles falls on which side is the practical starting point.
FMCSA also publishes inspection and crash data as public records, which is what makes external benchmarking of government fleets possible at all.