This synthesis will be of interest to staff of state departments of transportation responsible for highway routing, traffic engineering, traffic operations and signing, and maintenance. It will also be useful to state police, who may also be responsible for routing, and other enforcement personnel, as well as to emergency and fire personnel. The trucking industry will also find the information of value to their operations. Information is presented on the current practices of states for the highway routing of vehicles that transport hazardous materials. The Federal Highway Administration (FHWA) in 1994 issued Guidelines for Applying Criteria to Designate Routes for Transporting Hazardous Materials, which are used by agencies that elect to designate such routes. This report of the Transportation Research Board is based on information obtained from a survey of states concerning the routing of hazardous materials vehicles that asked respondents to rate the importance of 24 factors in the categories of roadway, environment, population, or other criteria in establishing routing policy. The survey also identified the principal agencies responsible for routing, as well as other agencies that typically participate in the routing plan. Enforcement and cost issues are discussed, as is risk assessment. This report presents a unique discussion of the issues as identified by interviews with trucking trade associations and other organizations involved with hazardous materials transport. In addition, technology applicable to more effective monitoring and enforcement is described. The appendices include commodity flow studies and route designation case studies for selected jurisdictions.