Efforts to implement the transportation control provisions of the Clean Air Act Amendments of 1970 have generated much discussion but little implementation of transportation measures to improve air quality. Reasons for this include conflicts over transportation priorities, inadequate institutional arrangements for combined transportation and air quality planning, and insufficient information concerning the relation between transportation and air quality. The Clean Air Act Amendments of 1977 provide a framework for handling these problems. However, important questions remain to be answered concerning organizational roles in transportation and air quality planning, the structure of the planning process, and the responsibilities of transportation and air quality decision makers./Author/