49 CFR § 655.31
Alcohol testing
November 18, 2020
(a) An employer shall establish a program that provides for testing for alcohol in the following circumstances: post-accident, reasonable suspicion, random, and return to duty/follow-up. An employer may also conduct pre-employment alcohol testing.
(b) Each employer shall prohibit a covered employee, while having an alcohol concentration of 0.04 or greater, from performing or continuing to perform a safety-sensitive function.