Key Definitions in 49 CFR Part 40

Short Answer

49 CFR § 40.3 defines the terms used consistently throughout Part 40, so that a word like "collector" or "verified test" means the same thing whether the context is a commercial driver, a pilot, or a railroad employee. This article organizes the definitions most relevant to the Return to Duty process: the people involved, the specimens and results being discussed, and the systems that track compliance.

Detailed Explanation

People and Roles

Term	Definition
SAP (Substance Abuse Professional)	Evaluates employees who violated a DOT drug or alcohol regulation and makes recommendations on education, treatment, follow up testing, and aftercare.
MRO (Medical Review Officer)	A licensed physician responsible for receiving and reviewing laboratory drug test results and evaluating medical explanations for certain results.
DER (Designated Employer Representative)	An employee authorized by the employer to remove employees from safety sensitive duty and make required decisions in testing and evaluation; receives test results. A service agent cannot act as a DER.
C/TPA (Consortium/Third Party Administrator)	A service agent that provides or coordinates drug and alcohol testing services for employers and performs administrative tasks; not itself an employer under Part 40.
Collector	The person who instructs and assists employees at a collection site and completes the Federal Custody and Control Form (CCF).
Employer	The entity subject to DOT testing regulations. Service agents are not employers.
Service agent	Any non-employer person or entity providing DOT testing related services, including collectors, Breath Alcohol Technicians (BATs), Screening Test Technicians (STTs), laboratories, MROs, SAPs, and C/TPAs.

Specimens and Results

Term	Definition
Primary specimen / Split specimen	The "A" bottle is tested first as the primary specimen. The "B" bottle, the split specimen, is retained and can be tested at the employee's request if the primary specimen is verified positive, adulterated, or substituted.
Adulterated specimen	A specimen shown, by the presence of a substance not normally found in human urine or an abnormal concentration of a naturally occurring substance, to have been altered.
Substituted specimen	A specimen with creatinine and specific gravity values so diminished or divergent that it is not consistent with normal human urine.
Dilute specimen	Urine with creatinine and specific gravity values lower than expected for normal human urine.
Negative result	A result showing no drug present, or a result below the applicable cutoff, on a valid specimen.
Non-negative specimen	A specimen result that is adulterated, substituted, positive, or invalid.
Verified test	A laboratory result that has undergone MRO review and received a final determination.
Cancelled test	A test with an uncorrected problem, or one that Part 40 otherwise requires to be cancelled. A cancelled test is neither positive nor negative.

Systems and Documentation

Term	Definition
Chain of custody	Documentation of specimen handling from collection through destruction, recorded on the Federal CCF.
Clearinghouse	The Commercial Driver's License Drug and Alcohol Clearinghouse, a database administered by FMCSA containing CDL holders' violations of Part 382 testing requirements and their Return to Duty status.
ODAPC	The Office of Drug and Alcohol Policy and Compliance, within the Office of the Secretary of DOT, which coordinates drug and alcohol testing program matters.
BAT (Breath Alcohol Technician)	Instructs and assists employees in alcohol testing and operates an Evidential Breath Testing device (EBT).
STT (Screening Test Technician)	Instructs and assists employees in alcohol testing and operates an Alcohol Screening Device (ASD).

Applicable Regulations

49 CFR § 40.3 is the definitions section of Part 40 and is the source for every term summarized in this article.

Professional Observation

In my experience, a surprising amount of confusion in the Return to Duty process traces back to a misunderstanding of a single term, most often the difference between a "non-negative" result and a confirmed positive, or the difference between the primary and split specimen. Reviewing the exact definition in 40.3 before drawing a conclusion about a specific test result is generally worth the extra few minutes.

Common Misconceptions

Misconception

A "non-negative" specimen means the same thing as a confirmed positive result.

Reality

A non-negative specimen is a broader category that includes adulterated, substituted, positive, and invalid results. Not every non-negative result is a confirmed positive; some require further MRO review or additional testing before a final determination is reached.

Why the Confusion Occurs

The word "non-negative" sounds like it simply means "positive" in everyday language, but Part 40 uses it as a technical category covering several distinct outcomes that each carry different consequences.

Frequently Asked Questions

Where can I find the full list of definitions in Part 40?

The complete set of definitions appears in 49 CFR § 40.3. This article summarizes the terms most relevant to the Return to Duty process rather than reproducing every definition in the section.

Do these definitions apply the same way across every DOT agency?

Yes. Because Part 40 is the shared procedural regulation adopted by all DOT agencies, these definitions apply consistently regardless of which agency's rule brought the employee into the testing program.

Primary Authorities

49 CFR § 40.3, Definitions

Need Help Understanding a Specific Term in Your Case?

A DOT qualified SAP can explain how these definitions apply to your specific test result or situation.

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Reviewed by: Perret deLapouyade, CEAP, SAP
Reviewed date: July 12, 2026
Updated date: July 12, 2026
BOK ID: BOK-0090