The goal of the AASHTO Strategic Highway Safety Plan is to reduce annual highway fatalities by 5,000 to 7,000. This goal can be achieved through the widespread application of low-cost, proven countermeasures that reduce the number of crashes on the nation's highways. This fourth volume of NCHRP Report 500, "Guidance for Implementation of the AASHTO Strategic Highway Safety Plan," provides strategies that can be employed to reduce the number of head-on crashes on two-lane roads. The report will be of particular interest to safety practitioners with responsibility for implementing programs to reduce injuries and fatalities on the highway system.