A DOT-regulated employee performs safety-sensitive functions covered by a DOT agency's drug and alcohol testing rule. They must take part in DOT testing under 49 CFR Part 40 and their agency's rule.

For FMCSA, this means drivers who operate a commercial motor vehicle that requires a CDL or CLP, for example a vehicle with a gross weight rating of 26,001 pounds or more, a vehicle designed to carry 16 or more passengers including the driver, or a vehicle carrying placarded hazardous materials (49 CFR 382.103, 49 CFR 383.5).

Other DOT agencies (FAA, FRA, FTA, PHMSA, and USCG) cover other safety-sensitive jobs. If you are unsure whether a job is covered, check the agency rule or ask your DER.