The opt out concept seems straightforward: If a state agreed to increase its own taxes and maintain the "federal system" (however defined), it would benefit from a commensurate decrease in federal fuel taxes. But the collection, attribution, and distribution of current federal fuel taxes complicates this proposition (setting aside the above-noted concerns about the federal role and investment needs). Fuel taxes are not collected directly from the end consumer; rather, they are paid at major distribution points (known as "the Rack") and then become part of the overall price passed down through the supply pipeline to the consumer. The fuel tax collections are attributed to the states based on estimates of fuel consumed in the states. The net receipts are distributed to the states predominantly according to formula apportionments, and less so through discretionary allocations, of the various federal spending programs. Thus, for a state to benefit in the desired manner from increasing its own taxes, it would need to receive some kind of rebate from the federal government-perhaps in the form of a block grant (without the federal requirements or other strings associated with current federal spending programs) calibrated to equal all or a portion of the amount of revenue estimated to result from its tax increase. While it should be possible to devise a rebate method consistent with the intent of various opt out proposals, the Commission strongly discourages Congress and the states from pursuing this action without fully under standing the overall impact on infrastructure investments needed to support an integrated and efficient national surface transportation network.