What Is Reasonable Suspicion Drug and Alcohol Testing? DOT Rules Explained

The definition, piece by piece

Every word in “specific, contemporaneous, articulable observations” does work. The rule uses the phrase for alcohol and again for controlled substances, and each word rules out a common shortcut.

What the rule requires of the observations

Specific: 49 CFR 382.307(a); A named observation, not a feeling. “Seemed off” fails. “Slurred the word dispatch twice and leaned on the trailer to stay upright at 6:40 a.m.” passes.
Contemporaneous: 49 CFR 382.307(d); Happening now. For alcohol, the observations must be made during, just before, or just after the period of the workday the driver must be in compliance, and the driver may be directed to test only in that window. Last week’s rumor is not contemporaneous.
Articulable: 49 CFR 382.307(f); It can be written down and signed. The rule makes that literal: a written record of the observations, signed by the supervisor who made them, within 24 hours of the behavior or before the results come back, whichever is earlier.
Appearance, behavior, speech, or body odors: 49 CFR 382.307(b); The four categories the rule names. For controlled substances, the observations may include indications of chronic and withdrawal effects, so a driver who is sweating, shaking, and agitated qualifies as much as one who is euphoric.
Made by a trained supervisor or company official: 49 CFR 382.307(c); The observer must have completed the §382.603 training: 60 minutes on alcohol misuse and 60 minutes on controlled substances. The person who makes the alcohol determination may not conduct the alcohol test.

Where it sits among the six DOT tests

Section 382.211, the refusal rule, lists all six tests a driver may not refuse. Five of them are triggered by events or schedules. Reasonable suspicion is triggered by a trained person. 49 CFR 382.211

The six FMCSA test types and what triggers each
Test	What triggers it	Rule
Pre-employment	Before a driver first performs safety-sensitive functions for the employer. Controlled substances only; a verified negative must be in hand before the driver is used.	49 CFR 382.301
Random	Unannounced selection by chance from the pool. The rule’s baseline annual minimums are 50 percent for controlled substances and 10 percent for alcohol, which FMCSA may adjust.	49 CFR 382.305
Post-accident	Fixed triggers after a crash: a fatality, or a citation to the driver plus an injury treated away from the scene or a vehicle towed.	49 CFR 382.303
Reasonable suspicion	A trained supervisor’s specific, contemporaneous, articulable observations of the driver’s appearance, behavior, speech, or body odors.	49 CFR 382.307
Return-to-duty	After a violation and the substance abuse professional’s process, before the driver resumes safety-sensitive functions, under Part 40 subpart O.	49 CFR 382.309
Follow-up	Unannounced tests after return to duty, on the schedule the substance abuse professional sets, under Part 40 subpart O.	49 CFR 382.311

Post-accident and reasonable suspicion are the two most often confused, because a crash and an impaired driver can arrive together. They have different triggers and different clocks; see Reasonable Suspicion vs. Post-Accident Testing.

Who can order it

A supervisor or company official who has completed the §382.603 training: at least 60 minutes on alcohol misuse and 60 minutes on controlled substances use. The title does not matter; the training and the authority to act do. A dispatcher, a terminal manager, a safety director, or an owner can all be the trained person. An untrained manager cannot, however senior. 49 CFR 382.307(c) 49 CFR 382.603

Two limits follow. The determination must rest on the trained person’s own observations, so a coworker’s report is a reason to go look, not a basis to order the test. And the person who makes the alcohol determination may not conduct the alcohol test. Who counts as a supervisor in each DOT mode, and what to do about owner-operators and HR, is covered in Who Needs Reasonable Suspicion Training?.

The process, start to finish

Observe and note the time. Write what you see, hear, and smell as you see it: slurred words, an odor on the breath, a stumble, pupils, agitation. Times matter later.
Decide. Do the observations fit the four categories, and are they happening now? If yes, the rule says the employer “shall require” the test. The decision is not optional once the facts are there. 49 CFR 382.307(a)–(b)
Tell the driver and remove them from safety-sensitive functions. State plainly that you have reasonable suspicion and that a DOT test is required. The driver does not drive from this point.
Arrange transport to the collection site. You have just decided this person may be impaired. Someone else drives.
Test on the clock. Alcohol within two hours; if not, record why and keep trying until eight hours, then stop and record why. The controlled substances collection has no fixed clock in §382.307; do it promptly and record any delay. 49 CFR 382.307(e)(1)
Sign the written record. Within 24 hours of the observed behavior or before the results are released, whichever comes first. 49 CFR 382.307(f)
Hold the driver out. No safety-sensitive functions until an alcohol test reads below 0.02 or 24 hours have passed since the determination, whether or not a test was ever given. 49 CFR 382.307(e)(2)
Act on the result. The table below covers each outcome.

The signs that justify the call, the things that do not count, and a free two-page observation form are in the reasonable suspicion checklist.

What each result means

Outcomes of a reasonable suspicion test

Alcohol under 0.02 and a negative drug result: 49 CFR 382.401(b)(2)–(3); The driver returns to duty. Keep the negative result for one year and the documents behind the decision to test for two years. The record of a well-documented negative is what protects the supervisor who made the call.
Alcohol 0.02 to 0.039: 49 CFR 382.505; Not a violation, but the driver may not perform safety-sensitive functions until the start of the next regularly scheduled duty period, and not less than 24 hours after the test. No action under Part 382 may be taken against the driver based on this result alone.
Alcohol 0.04 or greater, or a verified positive drug result: 49 CFR 382.501 49 CFR 40.285 49 CFR 382.705; A violation. The driver is removed from safety-sensitive functions, must complete a substance abuse professional evaluation and the return-to-duty process before resuming, and is subject to follow-up testing. The employer reports an alcohol result of 0.04 or greater to the Clearinghouse within three business days; the MRO reports the verified positive within two.
Refusal: 49 CFR 382.211 49 CFR 382.401(b)(1)(iii); Treated as a violation with the same consequences as a positive. Most refusals are reported by the employer within three business days; a few MRO-determined refusals are reported by the MRO. Documentation of the refusal is kept for five years.
No alcohol test within eight hours: 49 CFR 382.307(e)(1)–(3); Attempts stop and the record states why. The 24-hour hold still applies. Beyond it, the employer may not act under Part 382 on behavior and appearance alone, although the rule does not bar action the employer has independent authority to take.

Refusals have their own rules on what counts and who reports them. See When a Driver Refuses a Reasonable Suspicion Test.

Reasonable suspicion, reasonable cause, for cause

Three phrases describe tests that start with an observation. Two of them are DOT terms for the same thing. The third is not a DOT term at all.

Observation-based testing terms
Term	Who uses it	What it means	Rule
Reasonable suspicion	FMCSA; FTA; the alcohol rules of FAA and PHMSA	The observation-based DOT test described on this page.	49 CFR 382.307
Reasonable cause	The drug rules of FAA, PHMSA, and the Coast Guard	The same observation-based test under a different name. The Coast Guard asks for two supervisory observers where practicable.	14 CFR 120.115(c)49 CFR 199.113(c)46 CFR 16.250
For cause, probable cause	Company policies and non-DOT programs	Policy terms with no Part 382 meaning. A policy test is a non-DOT test: kept completely separate, run after the DOT test, never on DOT forms.	49 CFR 40.13

Related guides

Reasonable suspicion checklist and observation form: the signs, the clocks, and a free two-page form.
Reasonable suspicion vs. post-accident testing: different triggers, different clocks, and when both apply.
When a driver refuses a reasonable suspicion test: what counts as a refusal and what the employer must do next.
Who needs reasonable suspicion training: by DOT mode, with the edge cases.

Frequently asked questions

What is the difference between reasonable suspicion and random testing?

Random testing selects drivers by chance from a pool at annual minimum rates, with no observation needed and no notice. Reasonable suspicion testing is ordered for one driver because a trained supervisor observed specific, contemporaneous, articulable signs of alcohol misuse or drug use. Both are DOT tests run under Part 40 procedures, and a positive result or refusal carries the same consequences under either.

Can a coworker’s report trigger a reasonable suspicion test?

A report can and should prompt a trained supervisor to go and look. It cannot substitute for the supervisor’s own observations. Under 49 CFR 382.307(c) the observations that support the determination must be made by a supervisor or company official trained under §382.603, so the decision rests on what that person saw, heard, and smelled, not on what was relayed.

Can a driver refuse a reasonable suspicion test?

No. 49 CFR 382.211 prohibits refusing a reasonable suspicion test, and a refusal is treated as a violation with the same consequences as a positive result: removal from safety-sensitive functions, a substance abuse professional evaluation, and a report to the Clearinghouse. What counts as a refusal, and what the employer must do next, is covered in our guide on driver refusals.

Is reasonable suspicion the same as reasonable cause or for-cause testing?

Reasonable suspicion is FMCSA’s term and is also used by FTA and by the alcohol rules of other agencies. Reasonable cause is the term in the FAA, PHMSA, and Coast Guard drug rules for the same observation-based test. For cause and probable cause are company-policy and non-DOT terms. A non-DOT test ordered under policy must be kept completely separate from the DOT test and cannot replace it.

What happens if the alcohol test cannot be given within eight hours?

The employer stops trying and writes the reasons into the record. The driver still may not perform safety-sensitive functions until a test reads below 0.02 or 24 hours have passed since the determination. Beyond that hold, the employer may not take action under Part 382 against the driver based on behavior and appearance alone, although the rule does not bar action the employer has independent authority to take.

Does a reasonable suspicion test get reported to the Clearinghouse?

The result does, when it is a violation. The employer reports an alcohol confirmation result of 0.04 or greater and most refusals by the close of the third business day after learning of them; the MRO reports a verified positive, adulterated, or substituted drug result within two business days. A negative reasonable suspicion result, and an alcohol result under 0.04, are not reported to the Clearinghouse.

Can an employer run a non-DOT test instead of the DOT test?

No. Once a trained supervisor makes the determination under Part 382, the DOT test is mandatory. An employer may add a non-DOT test under its own policy, but 49 CFR 40.13 requires DOT and non-DOT tests to be completely separate, the DOT test to be completed first, and DOT forms never to be used for the non-DOT test.

Sources

Every citation on this page was checked against the eCFR text current as of October 30, 2026.