This synthesis was prepared to report on the state of the practice and to identify effective public involvement using limited resources. Basic information is offered here for transportation agencies to further their efforts in this area. This synthesis provides information about staff and agency experiences in the application of effective and cost-effective strategies and implementation techniques used to engage the public in the development of transportation plans and projects, as well as strategies found to be ineffective. It captures respondents' definitions of successful, effective, and cost-effective public involvement and reveals a rudimentary state of the practice in the areas of costs and measures of effectiveness. Although there appeared to be no clear cut definitions of responsibilities or implementation strategies, similarities and differences were identified in four areas - organizational structure, staffing, cost quantification, and process. Detailed appendices provide abstracts of the literature reviewed and document survey questionnaire interview responses.