Human factors account for most traffic accidents. The tractor-trailer, truck, bus, or car driver has a duty to keep a proper lookout, and safe driving requires vigilance and sustained attention, timely hazard detection, reasonable decision making to choose a hazard avoidance strategy, and prompt control responses (steering, braking, etc.). Inattention and driver impairment underlie most crashes. Impairment of attention, hazard detection, decision making, and reaction time are often due to fatigue, drowsiness, lack of sleep, cumulative sleep debt, the body’s circadian rhythms, and the effects of alcohol and other drugs. Other significant causes of inattention include texting or talking on a cell phone and other distractions. Dennis Wylie is an internationally recognized human factors expert concerning driver error; inattention and improper lookout; driver fatigue; car, truck and bus driver skill and knowledge requirements; driver and motor carrier standards of care; hours of service violations; circadian rhythms; sleep debt; impaired vigilance, alertness, decision making, reaction time, and control responses.