As planning for the interstate highway system was being completed, attention turned to increasing the productivity and efficiency of existing facilities. In planning for major new regional transportation facilities, many urban areas had neglected maintaining and upgrading other facilities. However, environmental concerns, the difficulty of building inner-city freeways, renewed interest in urban mass transit, and the energy crisis gave added impetus to the focus on more immediate problems. Signs were becoming evident of the changing emphasis to shorter-term time horizons and the corridor level in transportation planning. Gradually, planning shifted toward maximizing the use of the existing system with a minimum of new construction. Further, the connection was strengthened between long-term planning and the programming of projects (Weiner, 1982).
In October 1973, the Organization of Petroleum Exporting Countries (OPEC) embargoed oil shipments to the United States and, in doing so, began a new era in transportation planning. The importance of oil was so paramount to the economy, in particular, the transportation sector, that oil shortages and price increases gradually became one of the major issues in transportation planning (see Figure 8.1).
The immediate reaction to the oil embargo was to address the specific emergency. President Nixon signed the Emergency Petroleum Allocation Act of 1973 in November of that year, which established an official government allocation plan for gasoline and home heating fuel. The act regulated the distribution of refined petroleum products by freezing the supplier-purchaser relationships and