States determine their transportation investment priorities through structured planning processes. A key theme in the NCSL-AASHTO survey data was the tension between legislatures and DOTs about the appropriate level of legislative involvement or oversight in transportation planning. DOTs generally take the lead in conducting transportation planning activities and ensuring compliance with federal and state requirements, while legislative involvement and authority in planning varies greatly across states. At one end are Nebraska and Wyoming, which constitutionally prohibit the legislature from prioritizing specific road projects. At the other end are: Delaware, where legislators each determine the use of an annual authorization for transportation projects in their districts; Pennsylvania, where legislative leaders serve on the state Transportation Commission; and Wisconsin, where the Legislature is required by law to review and approve major highway projects. In at least 15 other states, the legislature actively reviews or approves DOT plans or programs, often as part of the budget process.

State DOTs generally take the lead in transportation planning activities; the extent of legislative authority and involvement in the process varies greatly across states.