Short Answer

49 CFR Part 40 sets the procedures that apply across the entire DOT drug and alcohol testing program, but each transportation industry is regulated day to day by its own DOT agency (sometimes called an "operating administration"). The definition of "DOT agency" in 49 CFR § 40.3 identifies which agencies apply Part 40 to their regulated industries. The table below describes each agency in general terms and the population it regulates.

DOT Agencies and Who They Regulate

FMCSA (Federal Motor Carrier Safety Administration)

Regulates commercial motor carriers and the safety-sensitive functions of Commercial Driver's License (CDL) holders, under 49 CFR Part 382.

FAA (Federal Aviation Administration)

Regulates safety-sensitive employees in aviation, including pilots and other flight crew and safety-sensitive maintenance and ground personnel.

FRA (Federal Railroad Administration)

Regulates safety-sensitive employees of railroads, including train crews and other covered service employees.

FTA (Federal Transit Administration)

Regulates safety-sensitive employees of public transit systems, including bus and rail transit operators and maintenance personnel.

PHMSA (Pipeline and Hazardous Materials Safety Administration)

Regulates safety-sensitive employees who operate or maintain pipeline facilities.

USCG (United States Coast Guard)

Regulates safety-sensitive employees in the maritime industry. Although the Coast Guard sits within the Department of Homeland Security rather than DOT, 49 CFR § 40.3 specifically provides that the Coast Guard is considered a "DOT agency" for drug testing purposes only, since the Coast Guard's own regulation does not incorporate Part 40 for its alcohol testing program.

NHTSA (National Highway Traffic Safety Administration)

Included within the Part 40 definition of DOT agency. NHTSA's day-to-day role in the Return to Duty process is smaller than that of FMCSA, FAA, FRA, FTA, PHMSA, or the Coast Guard, since it does not oversee a comparable population of safety-sensitive, testing-covered employees. Readers who need the precise scope of NHTSA's role should confirm it against the current regulatory text.

OST (Office of the Secretary of Transportation)

The umbrella office of the Department of Transportation. OST houses the Office of Drug and Alcohol Policy and Compliance (ODAPC), which coordinates drug and alcohol testing policy across all the modal agencies listed above.

Applicable Regulations

• 49 CFR § 40.3, Definitions (DOT agency)
• 49 CFR § 382, FMCSA-specific drug and alcohol testing requirements for CDL holders

Professional Observation

Many drivers assume that "DOT testing" is a single uniform program. In practice, Part 40 sets the shared procedures, but each modal agency layers its own rules on top, including different safety-sensitive job definitions and, in some cases, different testing thresholds. When a question depends on which agency regulates a specific job, it is worth confirming the applicable agency rule rather than assuming FMCSA's rules apply everywhere.

Related Articles

• Which DOT Agencies Use the Return to Duty Process?
• Who Is Required to Complete the Return to Duty Process?
• What Is the FMCSA Drug and Alcohol Clearinghouse?
• Understanding 49 CFR Part 40
• Common DOT Return to Duty Acronyms

Primary Authorities

• 49 CFR § 40.3, Definitions
• 49 CFR § 382, FMCSA controlled substances and alcohol use and testing

Not Sure Which Agency's Rules Apply to You?

If you are unsure which DOT agency regulates your position, a DOT qualified Substance Abuse Professional can help clarify which rules apply to your Return to Duty process.

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