The 1991 highway authorization act, known as ISTEA, also created a number of requirements for coordination of planning with Clean Air Act requirements. These provisions often include penalties for non-compliance that can result in loss of federal highway funds. One example includes the requirement for centralized auto test centers in ozone non-attainment areas. Aggressive efforts by several states to challenge those requirements, including efforts by Michigan Governor John Engler, have led the EPA to back away from more onerous provisions. However there are a number of other ISTEA and Clean Air Act planning requirements that the state should also challenge.

For instance, the Act requires extensive planning and documentation to add traffic lanes in non-attainment areas, and eliminates needed flexibility. Projects that will increase single occupancy vehicle (SOV) traffic must be included in state or Metropolitan Planning Organizations' (MPO) long range and three year plans. Furthermore, the state must demonstrate quantitatively why travel demand management and mass transportation operations cannot eliminate the need for the project.49 The state then must also make commitments to reduce SOV traffic, and must demonstrate that an approved car pooling program is in place on the corridor.

ISTEA and the Clean Air Act also require states to demonstrate that all projects in non-attainment areas are included in "conforming" long range plans, and that such plans conform with the state's implementation plan for target pollution reductions. The resulting bureaucratic maze is enough to stop almost any project from progressing.