49 CFR Part 40 Explained in Plain English

Short answer: 49 CFR Part 40 is the U.S. Department of Transportation's rulebook for how every DOT-regulated drug and alcohol test must be conducted. It applies to trucking, aviation, rail, transit, pipeline, and maritime — including every CDL driver and owner-operator. If a test is a "DOT test," it followed Part 40.

What is 49 CFR Part 40?

Part 40 of Title 49 of the Code of Federal Regulations is the single, government-wide procedural standard for DOT drug and alcohol testing. It's written and maintained by the DOT's Office of Drug and Alcohol Policy and Compliance (ODAPC). Every DOT agency — FMCSA (trucking), FAA (aviation), FRA (rail), FTA (transit), PHMSA (pipeline), and USCG (maritime) — sits on top of Part 40 and adds its own rules for who has to test and when. Part 40 controls the how.

Who does Part 40 apply to?

• Every CDL driver in a safety-sensitive role, including owner-operators
• Every motor carrier and every C/TPA (Consortium/Third-Party Administrator)
• Every collection site, laboratory, MRO (Medical Review Officer), SAP (Substance Abuse Professional), and BAT (Breath Alcohol Technician)

If any of those touch a DOT test, they follow Part 40. Non-DOT workplace testing does not.

The six testing scenarios Part 40 covers

1. Pre-employment — before a driver first performs a safety-sensitive function.
2. Random — unannounced selection from a pool at the FMCSA's annual minimum rate. See our random pool guide for how selections actually work.
3. Post-accident — after a qualifying crash, on a strict timeline.
4. Reasonable suspicion — when a trained supervisor observes specific, articulable signs of impairment.
5. Return-to-duty — one observed test after completing the SAP process.
6. Follow-up — a SAP-directed schedule of at least six unannounced tests in the first 12 months after RTD.

The panel: what Part 40 tests for

The DOT drug panel is a urine 5-panel: marijuana (THC), cocaine, opiates (including oxycodone, hydrocodone, hydromorphone, and oxymorphone), amphetamines/methamphetamine (including MDMA), and PCP. As of June 2023, DOT also authorizes oral fluid testing as an alternative specimen — but a lab must be HHS-certified for oral fluid before an employer can use it. Alcohol is tested separately by a breath or saliva screen followed, if positive, by an evidential breath test.

Cutoff levels and the MRO

A positive lab result is not a "failed DOT drug test" until a Medical Review Officer verifies it. The MRO is a licensed physician trained in Part 40. They contact the driver, review any legitimate medical explanation (a valid prescription for oxycodone, for example), and only then verify the result as positive or negative. Drivers have the right to a split-specimen retest at a second HHS-certified lab if they dispute the result.

Refusals under Part 40

A refusal counts the same as a verified positive. Refusals include:

• Failing to appear for a test in a reasonable time after being directed
• Leaving the collection site before the process is complete
• Failing to provide a sufficient specimen without a valid medical reason
• Adulterating or substituting a specimen
• Refusing to sign the certification on the Custody and Control Form

Part 40 and the FMCSA Clearinghouse

The Clearinghouse is an FMCSA rule (49 CFR Part 382), but every violation reported to it is generated by a Part 40 test. If you want the full picture of how positives and refusals get reported and how return-to-duty works, read our FMCSA Clearinghouse driver's guide.

What owner-operators actually have to do

You don't need to memorize Part 40. You need to be enrolled in a compliant program run by a C/TPA that does follow Part 40 end-to-end. That's what a consortium is for — pool management, collection-site network, MRO services, SAP referrals, and Clearinghouse reporting all handled to Part 40 standards. Our pricing is $150/year for owner-operators and $200/year for small fleets, plus drug tests.

Where to read Part 40 yourself

The official text lives at ecfr.gov/current/title-49/subtitle-A/part-40. ODAPC also publishes plain-language guidance and Q&A documents that clarify how specific subparts apply in real situations.

How Part 40 has changed recently

Part 40 is not a static document. Two updates matter most for owner-operators and small fleets:

• Oral fluid testing (2023). DOT authorized saliva as a testing specimen alongside urine. In practice, HHS lab certification for oral fluid rolled out slowly, so most tests are still urine — but employers who want observed-collection alternatives can now use oral fluid where available. This was the biggest procedural change in years.
• Clearinghouse-II CDL downgrade (2024). This is technically a Part 382 update, but it enforces every Part 40 positive with unprecedented weight. Once your Part-40 positive is reported, the state pulls your CDL. There is no separating the two rulebooks anymore in practice.

Fentanyl and synthetic-opioid panel expansion has been discussed at every DOT rulemaking cycle for the last several years and may appear in a future amendment. Follow ODAPC's rulemaking dockets if you want early warning.

Common Part 40 mistakes small carriers make

• Using a non-Part-40 collection site. Occupational-health clinics that do workplace testing don't always run DOT protocols. If the collection isn't done under Part 40, the result isn't a DOT result — the test doesn't count and you may still be non-compliant.
• Missing the MRO step. A lab-only positive is not a "failed DOT test." Reporting anything to the Clearinghouse before the MRO verifies is a Part 40 violation and can expose the carrier to liability.
• DIY random selection. Owner-operators sometimes think they can put their own name in a hat. FMCSA requires a C/TPA — a third party — because the whole point of "random" is that the tested person can't control the selection.
• Skipping the SAP. After a positive, some drivers try to just wait it out or find a carrier that "won't ask." Every DOT carrier is required to query the Clearinghouse. Trying to skip the SAP is a compliance dead-end.

Recordkeeping under Part 40

Carriers must retain records for varying periods depending on document type:

• 5 years: positive tests, refusals, evaluations by SAPs, follow-up testing schedules, calibration records for alcohol testing devices
• 2 years: collection process records, negative and cancelled test results
• 1 year: negative alcohol test results
• Indefinitely: the annual MIS summary a carrier submits when FMCSA requests it

Owner-operators enrolled in a compliant consortium have their C/TPA maintain most of these records. That's a big part of what you're paying $150/year for.