49 CFR Part 199 (PHMSA drug and alcohol testing regulation) and 49 CFR Part 40 (DOT drug and alcohol testing regulation) require operators to conduct drug and alcohol testing of covered employees who perform operation, maintenance, or emergency-response functions regulated by 49 CFR Parts 192, 193, or 195.

49 CFR Part 199 (PHMSA Regulation)

49 CFR Part 40 (DOT Regulation)