This synthesis report will be of special interest to maintenance, construction, and traffic engineers and others interested in the use of impact attenuation devices or crash cushions for highway operations. Information is provided on the performance and operational experience of 13 crash cushion devices in current use in the United States and Canada, including physical characteristics, test results, and guidelines for use. Both permanent and temporary devices are included. Crash cushions can provide a cost-effective method for reducing or alleviating motor vehicle related injuries or fatalities, which constitute a major societal cost. This report of the Transportation Research Board presents information on the physical and impact performance characteristics of 13 crash cushions in current use in North America. Information on performance evaluation guidelines, physical characteristics, performance characteristics, selection considerations, and the operational experience of individual designs for crash cushions is provided. The synthesis concludes with possible future trends for crash cushions and appendices containing the crash test requirements of NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features, a crash cushion glossary, and a bibliography.