State legislatures exercise significant power over state revenue sources and appropriations. Only five states and the District of Columbia reported that any state funds flow directly from a revenue source to the DOT without legislative appropriation. The real power of legislatures-or DOTs-to allocate state funds, however, is bounded by restrictions on the use of transportation revenues. For example, 23 states have constitutional provisions-and three have statutory provisions-that restrict use of state fuel tax revenues exclusively to highway and road purposes. Most other states dedicate these and other transportation-related revenues to general or multimodal transportation purposes, with a few limited exceptions. In addition, 35 states reported they have provisions that direct use of the funds or accounts to which transportation revenues are deposited. At least six states also explicitly prohibit diversion or transfer of transportation revenues to other purposes.

In about half the states, state fuel tax revenues are restricted exclusively to highway and road purposes; most other states dedicate these and other transportation-related revenues to general or multimodal transportation purposes.