D.C. Code § 1-620.11

In compliance with federal regulations issued pursuant to 49 U.S.C. § 31306 , the Mayor and each personnel authority shall adopt and administer a program and issue rules for conducting pre-employment, reasonable suspicion, random, post-accident, return-to-duty, and follow-up testing of employees who are employed as drivers of commercial motor vehicles, or who are candidates for such employment, for the use of alcohol and controlled substances.