In safety sensitive occupations, an alert worker is the best defense against incidents. Workers may experience alertness deficits and elevated safety risk due to fatigue, medical conditions and medications that cause drowsiness. This session presents an approach that aids in the detection of alertness deficits to ensure workers are sufficiently alert to be safe on the job. The approach is based on a widely recognized, heavily validated, standard measure of behavioral alertness. The session will present an overview of the scientific basis of this approach as well as results from a program recently implemented at ExxonMobil to aid in the detection of alertness deficits in safety sensitive workers.