Drowsy driving is a significant contributor to death and injury crashes on our Nation's highways, accounting for more than 80,000 crashes and 850 fatalities per year. The successful detection of drowsiness is a crucial step in implementing mitigation strategies to reduce the cost to society of drowsy driving. Despite persistent efforts at the local, state, and federal levels, alcohol-impaired driving crashes also contribute to approximately 31% of all traffic fatalities. Although regulatory and educational approaches have helped reduce alcohol-related fatalities, other approaches merit investigation. This book discusses the feasibility of vehicle-based sensors to detect both drowsy driving and alcohol-impaired driving.