The intervention involves primary and secondary levels at the point of intervention. Primary efforts aim at stopping people from getting too drunk to drive. This includes the use of breathalyzers in bars to help people stay below the legal limit for impaired driving. Secondary intervention aims at keeping impaired persons from driving. This involves putting devices on vehicles to prevent their being driven by impaired persons. Overall strategies for countering drunk driving include legal efforts, education, and medical treatment. Legal efforts focus on the minimum drinking age, the driver-licensing age, sanctions for drunk driving, and law enforcement techniques for deterring and detecting drunk driving. Education may involve a mass media campaign targeting all drivers or high-risk drivers. Long-term education for preventing impaired driving must be provided in the schools. Medical treatment involves identifying persons with alcohol dependency and providing treatment with proven effectiveness. Another strategy is a systems approach that involves a combination of the legal, educational, and treatment approaches.