Because a supervisor’s ability to act on a reasonable suspicion is the only mechanism in 49 CFR §382.307 that triggers an unscheduled test. The §382.603 training ensures that supervisors can recognize the physical, behavioral, speech, and performance indicators of alcohol misuse and controlled-substance use, and that they can document those observations defensibly. Without this training, a supervisor cannot lawfully direct a reasonable-suspicion test — and without that training, the program’s deterrent effect collapses.