Since the 1950s, America's infrastructure development and maintenance program has depended in great part on an end-user tax on fuel. More efficient auto and heavy-truck fuel consumption, combined with an ever-enlarging and aging infrastructure system, have brought us to the limit of the end-user fuel tax as a sole source of revenue. The public has little appetite for increasing the end-user sales tax to replenish the Highway Trust Fund. Although industry and government have pushed new sources of financing and tried to cut costs, little real progress will be made without a new source of revenue, and the Highway Trust Fund will continue to erode.