Substance abuse including alcohol and drug use impairs judgment, coordination, and reaction time, creating serious safety hazards. Impaired workers present hazards to themselves and coworkers. Construction work involves heavy equipment, heights, and serious hazards; impairment is particularly dangerous. Alcohol impairs balance and coordination within minutes and affects judgment. Even small amounts of alcohol reduce reaction time. Marijuana impairs judgment and reaction time for several hours after use. Opioids and other drugs cause drowsiness, impaired judgment, and coordination loss. Prescription medications can impair performance; workers should be warned of safety effects. Stimulants including methamphetamine and cocaine impair judgment while increasing risk-taking behavior. Construction employers must have substance abuse policies that are consistently enforced. Drug testing at hire and random testing during employment identifies impaired workers. Testing must comply with applicable laws; some states restrict drug testing. Post-incident testing may identify substance abuse as a factor in incidents. Employees with substance abuse problems should be offered employee assistance programs (EAP) providing treatment and support. Treatment should be encouraged over punishment when possible. Return-to-work protocols following treatment verify the worker is fit for duty. Workers appearing impaired should not be allowed to work. Impairment signs include slurred speech, drowsiness, unusual behavior, or tremors. If suspected, the worker should be referred for evaluation. Coworkers observing impaired behavior should report it to supervisors. Zero-tolerance policies support enforcement of substance-abuse prohibitions. Education on substance abuse hazards helps workers understand the seriousness.