Over the last 15 years, Congress has consistently increased authorizations for HTF spending. These budget authorizations provide the basis for future obligations (commitments) and outlays (expenditures). Exhibit 2-11 shows that from the first year of the Intermodal Surface Transportation Efficiency Act (ISTEA, 1992) to the final year of SAFETEA-LU (2009), federal highway budget authorizations increased by 46 percent and federal transit budget authorizations increased by 85 percent in 2008 dollars. (Note that a portion of federal transit spending is funded from the General Fund instead of the HTF—about 15-20 percent in recent years.) The apparent 17-year growth largely disappears, however, when adjusted for the increases in vehicle and passenger miles traveled. After accounting for the overall growth

Source: FHWA Fact Sheets on Highway Provisions

in the economy, highway authorizations as a percentage of GDP have decreased by 6 percent since the first year of ISTEA, while transit authorizations have still grown, Put only by 13 percent.25

Recent federal authorizing legislation for surface transportation has provided budget authority for highway and transit programs covering six years at a time. This budget authority, which is