A reasonable-suspicion test is one of the few moments in an FMCSA drug-and-alcohol program where a single person's judgment, formed in minutes, creates a legal record. Getting the standard right matters, and a great deal of what circulates as "the rule" is not in the regulation at all.
The standard the regulation actually sets
Under 49 CFR § 382.307, an employer must require a driver to submit to a test when a trained supervisor or company official has reasonable suspicion to believe the driver has violated the prohibitions of Part 382 subpart B.
The determination must be based on specific, contemporaneous, articulable observations concerning the appearance, behavior, speech or body odors of the driver.
Read those three words carefully, because each is doing work:
- Specific — "he seemed off" is not an observation. "His speech was slurred and he could not track the conversation" is.
- Contemporaneous — formed at the time, not reconstructed a week later from memory.
- Articulable — capable of being stated in words, by the person who saw it.
What the regulation does not say
Two beliefs come up constantly in training rooms, and neither is in the text.
There is no required number of signs. Federal law does not say that one indicator is legally insufficient, and it does not say a "cluster" is always required. The decision rests on specific, contemporaneous, articulable observations and the facts of the situation. A single, clearly articulated observation can support a determination; four vague impressions may not.
The written report does not have to come first. Nothing requires a supervisor to finish paperwork before acting on an immediate safety concern or before testing begins. The sequence in practice is: identify the specific observations, follow the employer's safety and testing procedures, then complete the record.
Who may make the determination
The determination must be made by a supervisor or company official who has received the training required by 49 CFR § 382.603 — at least 60 minutes on alcohol misuse indicators and at least 60 minutes on controlled-substances use indicators.
That training requirement is not a formality. It is the thing that makes the person's observation admissible as the basis for a federal test.
An important separation: the person who makes the observation is generally not the person who evaluates the test result. The laboratory analyzes the specimen. The Medical Review Officer reviews and verifies drug-test results. Qualified alcohol-testing personnel conduct alcohol tests. The employer and the Designated Employer Representative take the actions assigned to the employer.
Documenting the observation
The written record must identify the specific observations that supported the decision. It must be completed and signed by the supervisor within 24 hours of the observed behavior, or before the test results are released, whichever occurs first.
A useful discipline when writing it: a reader who was not present should be able to picture what you saw. Compare these two entries.
Driver appeared to be under the influence. Sent for testing.
At approximately 0715 in the yard, driver's speech was slurred and he repeated the same question three times. He was unsteady stepping down from the cab and braced against the door. A sweet chemical odor was noticeable at conversational distance.
The first records a conclusion. The second records observations, which is what the regulation asks for — and which is what will still make sense to a reader two years from now.
The alcohol timing rule is separate
Keep the alcohol-specific observation window distinct from the controlled-substances standard. Under § 382.307, alcohol testing on reasonable suspicion is only authorized during, just before, or just after the driver performs safety-sensitive functions. There are also specific requirements about what happens if the alcohol test is not administered within two hours, and within eight hours.
Controlled-substances reasonable-suspicion testing does not carry that same window. Treating the two as one rule is a common and consequential error.
A note on refusals
A refusal to submit is a separate DOT violation with its own consequences, including removal from safety-sensitive functions and entry into the return-to-duty process. It is not a verified positive test result, and describing it as "exactly the same as a positive" is inaccurate. Confirm who the decision-maker is in any refusal scenario before acting.
What good practice looks like
- Train the people who will actually make determinations, and keep the training records.
- Give supervisors a structured observation form that prompts for appearance, behavior, speech and odor separately.
- Record observations, not conclusions.
- Keep the immediate safety action and the paperwork in the right order — act, then document within the window.
- Capture the reasoning at the time it was made rather than reconstructing it later.
FAQ
How many signs are required for reasonable suspicion?
Federal law does not require a specific number of signs. The determination must be based on specific, contemporaneous, articulable observations concerning the driver's appearance, behavior, speech or body odors, and on the facts of the situation.
Does the written report have to be finished before testing begins?
No. Nothing requires the written record to be completed before immediate safety action or before testing starts. The supervisor identifies the specific observations, follows the employer's safety and testing procedures, and then completes and signs the written record within 24 hours of the observed behavior or before the test results are released, whichever occurs first.
Who is allowed to make a reasonable-suspicion determination?
A supervisor or company official who has completed the training required by 49 CFR 382.603 — at least 60 minutes on alcohol misuse indicators and at least 60 minutes on controlled-substances use indicators.
Is a refusal to test treated the same as a positive result?
No. A refusal is a separate DOT violation that can trigger removal from safety-sensitive functions and the return-to-duty process. It is not a verified positive test result.
Does the same timing rule apply to drug and alcohol reasonable-suspicion tests?
No. Alcohol testing on reasonable suspicion is authorized only during, just before, or just after the driver performs safety-sensitive functions, with specific requirements at the two-hour and eight-hour marks. Controlled-substances testing does not carry that same window.
This article describes federal requirements under 49 CFR Parts 40 and 382 and is provided for general information. It is not legal advice. Employers remain responsible for their own compliance decisions and should consult qualified counsel or a DOT specialist about their specific circumstances.