49 CFR § 219.101 - Alcohol and drug use prohibited.
(a) Prohibitions. Except as provided in § 219.103 -
(i) Under the influence of or impaired by alcohol;
(ii) Having 0.04 or more alcohol concentration in the breath or blood; or
(iii) Under the influence of or impaired by any controlled substance.
(3) No regulated employee may use alcohol for whichever is the lesser of the following periods:
(i) Within four hours of reporting for regulated service; or
(i) No regulated employee tested under the provisions of this part whose Federal test result indicates an alcohol concentration of 0.02 or greater but less than 0.04 may perform or continue to perform regulated service for a railroad, nor may a railroad permit the regulated employee to perform or continue to perform regulated service, until the start of the regulated employee's next regularly scheduled duty period, but not less than eight hours following administration of the test.
(ii) Nothing in this section prohibits a railroad from taking further action under its own independent company authority when a regulated employee tested under the provisions of this part has a Federal test result indicating an alcohol concentration of 0.02 or greater, but less than 0.04. However, while a Federal test result of 0.02 or greater but less than 0.04 is a positive test and may be a violation of a railroad's operating rules, it is not a violation of this section and cannot be used to decertify an engineer under part 240 of this chapter or a conductor under part 242 of this chapter.
(5) If an employee tested under the provisions of this part has a test result indicating an alcohol concentration below 0.02, the test is negative and is not evidence of alcohol misuse. A railroad may not use a Federal test result below 0.02 either as evidence in a company proceeding or as a basis for subsequent testing under company authority. A railroad may take further action to compel cooperation in other breath or body fluid testing only if it has an independent basis for doing so. An independent basis for subsequent company authority testing will exist only when, after having a negative Federal reasonable suspicion alcohol test result, the employee exhibits additional or continuing signs and symptoms of alcohol use. If a company authority test then indicates a violation of the railroad's operating rules, this result is independent of the Federal test result and must stand on its own merits.
(b) Controlled substance. “Controlled substance” is defined by § 219.5. Controlled substances are grouped as follows: marijuana, narcotics (such as heroin and codeine), stimulants (such as cocaine and amphetamines), depressants (such as barbiturates and minor tranquilizers), and hallucinogens (such as the drugs known as PCP and LSD). Controlled substances include illicit drugs (Schedule I), drugs that are required to be distributed only by a medical practitioner's prescription or other authorization (Schedules II through IV, and some drugs on Schedule V), and certain preparations for which distribution is through documented over the counter sales (Schedule V only).
(c) Railroad rules. Nothing in this section restricts a railroad from imposing an absolute prohibition on the presence of alcohol or any drug in the body fluids of persons in its employ, whether in furtherance of the purpose of this part or for other purposes.
(d) Construction. This section may not be construed to prohibit the presence of an unopened container of an alcoholic beverage in a private motor vehicle that is not subject to use in the business of the railroad; nor may it be construed to restrict a railroad from prohibiting such presence under its own rules.
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