A bipartisan Congressional National Surface Transportation Infrastructure Financing Commission just completed a two-year study. Their report predicts that only $32B annually will be raised by current fuel taxes in future years whereas $100B will be required to meet US transportation needs.
Background
Congress temporarily patched $8B shortfall caused by a slump in fuel tax revenue
Stimulus bill devotes $45B+ to transportation projects
National Surface Transportation Infrastructure Financing Commission did recent study
Congress often uses commissions to generate solutions to politically touchy problems