A $6 million contract awarded by the Pennsylvania Turnpike Commission to a Missouri company will lead the way to all-electronic tolling across the turnpike and the elimination of toll plazas. It's also the precursor of an entirely new way of assessing transportation taxes, which is why Congress should mandate interstate cooperation in the establishment of such systems.

The turnpike already has implemented a two-tiered pricing system, with cash tolls being substantially higher than those assessed to E-ZPass customers, in order to help cover the higher collection costs associated with cash. The gap between cash and electronic rates will grow as the turnpike tries to convince more travelers to use E-ZPass.

Under the turnpike's plan, toll plazas will be replaced with automatic readers that record pre-paid E-ZPass tolls while recording the license numbers of non-E-ZPass vehicles. Owners of those vehicles will be billed. Development of such a system will be good for consumers because reducing the turnpike's toll-collection expenses will help to minimize toll increases, upon which the state relies not only for turnpike maintenance but for interstate highway maintenance.

The immediate drawback of the idea is that the state government has no authority to bill out-of-state drivers, including truck and bus operators, who do not use E-ZPass.

That's why Congress should take up the issue under its authority to regulate interstate commerce. Many states intend to establish all-electronic tolling, and must have the authority to bill across state lines.

Moreover, the electronic tolling system also will be the foundation of a new system of transportation tax collection that the federal government itself ultimately will have to use.

There are more than 50,000 all-electric cars on the nation's highways, along with a growing number of hybrid vehicles that use far less gasoline than other vehicles. Advances in battery technology promise to increase the number of vehicles that generate reduced or no transportation taxes, which come primarily from gasoline and diesel fuel sales, even as they continue to use the highways.

At some point the government will have to convert to a system that taxes actual miles driven, rather than amount of fuel purchased. That will require electronic systems akin to the E-ZPass.

Congress should take up interstate toll collection as a means to help the states minimize tolls, and to prepare for the future of transportation funding at the state and federal levels.