83 changes in the transportation system, the act strongly encouraged the preparation of transportation elements of the SIP by metropolitan planning organizations. These local planning organizations were responsible for developing the transportation control measure element of the SIP (Cooper and Hidinger, 1980). From 1978 to 1980, the DOT and EPA, after long negotiations, jointly issued several policy documents to implement the Clean Air Act's transportation requirements. One of these, signed in June 1978, was a “Memorandum of Understanding" that established the means by which the DOT and the EPA would assure the integration of transportation and air quality planning. A second one issued also in June 1978, “Transportation Air Quality Planning Guidelines" described the acceptable planning process to satisfy the requirements. Another, in March 1980, was a notice containing guidelines for receiving air quality planning grants under section 175 of the act (Cooper and Hidinger, 1980). In January 1981 DOT issued regulations on air quality conformance and priority procedures for use in federal highway and transit programs. The regulations required that transportation plans, programs, and projects conform with the approved SIPs in areas that had not met ambient air quality standards, termed “nonattainment areas.” In those areas, priority for transportation funds was to be given to “transportation control measures" (TCMs) that contributed to reducing air pollution emissions from transportation sources. Where an area's transportation plan or program was not in conformance with the SIP, “sanctions" were to be applied that prohibited the use of federal funds on major transportation projects (U.S. Dept. of Transportation, 1981b). The 1977 Clean Air Act Amendments certainly gave impetus to short-range planning and transportation system management strategies. They also added a new dimension to the institutional and analytical complexity of the planning process.