The process by which Congress enacts funding for transportation programs involves the division of responsibilities among four sets of committees in both the House of Representatives and the Senate. The first set of committees includes the Housc Committee on Transportation and Infrastructure and the Senate Committees on Banking, Housing, and Urban Affairs; on Commerce, Science, and Transportation; and on Environment and Public Works. These are the authorizing committees that provide the actual contract authority for transportation programs; however, they are not responsible for the actual outlay of funding from the treasury.

The contract authority is allocated to the appropriations committees in both houses, which make the actual outlays, as discretionary. These committees place limits on the amount of contract authority that can actually be obligated by transportation programs for the year. Meanwhile, the tax-writing committees (including the House Ways and Means Committee and the Senate Finance Committee) control the transportation trust funds by limiting spending from the trust funds to the amounts approved in the authorization bills. Finally, the congressional budget committees play a role by setting annual spending aggregates, allocating funds to committees, and making determinations to enforce budget allocations. This network of committees dealing with transportation funding ultimately serves to obscure accountability for the funding and makes the process one of the most complex funding schemes in Congress.