GAO discussed key issues affecting the implementation of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA). GAO noted that: (1) total revenues to the highway account will not meet authorized funding by the end of the ISTEA authorization period; (2) projected fuel and other highway-related tax receipts through fiscal year 1999 will be $3.2 billion lower than amounts projected in July 1992; (3) the balance of the highway account will be drawn down earlier than anticipated if the administration's economic package and long-term investment strategy are enacted; (4) recent surface transportation legislative actions have generated a proliferation in funds authorized for highway demonstration projects; (5) authorization of new demonstration projects could be problematic if federal funds are not sufficient to complete projects or additional funds are authorized for approved, underfunded demonstration projects; (6) demonstration projects often provide limited benefits; and (7) states and local governments have made limited use of flexible ISTEA funding provisions.