Substance Abuse Professional Services The DOT (Department of Transportation) requires companies that employ individuals who hold commercial driver licenses (DCLs) to perform random, pre-employment, post accident, reasonable suspicion, and return to duty drug and alcohol tests. Under CFR 49 Part 40, any individual who tests positive for drugs and/or alcohol must be referred to a qualified S.A.P. (Substance ABuse Professional) who will provide a comprehensive face-to-face assessment and clinical evaluation and recommend a course of treatment.