This special investigation report looks at one of the most serious types of highway accidents-collisions involving vehicles traveling the wrong way on high-speed divided highways. The goal of this investigative project is to identify relevant safety recommendations to prevent wrong-way collisions on such highways and access ramps. The investigations included in the report take a focused view of the driver and highway issues affecting wrong-way collisions. The report addresses the following safety issues concerning wrong-way driving: driver impairment, primarily from alcohol use, with consideration of older driver issues and possible drug involvement; the need to establish, through traffic control devices and highway design, distinctly different views for motorists approaching entrance and exit ramps; monitoring and intervention programs for wrong-way collisions; and in-vehicle driver support systems.