"An oil tax would have appealing features: It is likely to be relatively easy to administer because it would be collected at the refinery or ports, it would spread the cost of transportation funding across a larger pool of users than current taxes do, it could account for the external costs associated with oil production and consumption, and it could be designed in ways to provide consistent funding for transportation infrastructure and other spending priorities," according to the report by the Santa Monica, California-based nonprofit institution.

Federal spending on transportation infrastructure outpaced revenues from federal gasoline and diesel taxes in 2009. The report points out those taxes are not indexed to inflation and have not been raised since 1993. In addition, increasing vehicle fuel efficiency has resulted in drivers spending less money buying gasoline and diesel, and thus paying less fuel tax into the Highway Trust Fund that finances road construction and transit improvements.

A single tax on oil and imported refined oil products, according to the report, could address those shortcomings on a couple of fronts. Along with simplifying the tax system, an oil tax could be adjusted automatically to better fund appropriated transportation expenditures.

"By tying tax rates to appropriated monies for transportation spending, and adjusting those rates to changes in world market oil prices, the tax would ensure that future revenue keep pace with transportation expenditures," the report contends.

An oil tax could shift external costs associated with oil to its producers and consumers rather than the general public. The tax could also help finance national security expenditures that result from protecting oil-producing nations and sea lanes used to import oil.

The report acknowledges that the enactment of a percentage tax on crude oil would be challenging in light of widespread antitax sentiment in Congress. Rand notes, however, that national security concerns could help make that tax more palatable than others.

"Phasing in might also help garner public acceptance for an oil tax," according to the report. "Ensuring that the transition away from motor-fuel taxes toward a unified oil tax is gradual could make the tax more politically feasible."

The 49-page report, "The Option of an Oil Tax to Fund Transportation and Infrastructure," is available at bit.ly/Rand-Report.