Two recent articles have mentioned tolls on local highways as a means of financing highway improvements. The first {Metro, Nov. 29} discussed a proposal by the Council of Governments' staff to use tolls on the Beltway river crossings. The second {Metro, Jan. 2} raised the toll question in the context of regional transportation finance in the present straitened circumstances.

Both articles omitted a critical point. Current technology allows for toll collection without requiring cars to stop or even slow down. With automatic vehicle identification technology, vehicles are outfitted with a device called a transponder, which broadcasts an identifying code to a roadside device. The charge may be collected through billing a credit card, drawing down a balance in a credit account (as with cash machines) or charging against a farecard, as in the Washington Metro system. Vehicles without transponders, or drivers who do not wish to be identified in a specific instance, pass through conventional toll booths. In practice, though, most people opt for the transponder, so only a few vehicles require toll booths, and they can leave the traffic stream, pay and rejoin it -- all without significantly disrupting traffic.

This AVI method of toll collection is in use in Texas and Mississippi. It will be installed on the Dulles Toll Road during the next year and used on the extension of the Dulles Toll Road to Leesburg.

AVI makes toll financing much more feasible. Toll booths are labor-intensive and cause congestion; governments generally prefer easy-to-collect user fees, like gas taxes, to finance highways. But the gas tax is a poor measure of consumers' willingness to pay for improved highways. Consumers generally vote for improved highways only indirectly, at the ballot box. AVI will allow them to express their willingness to pay directly through a toll. And drivers are willing to pay, judging from traffic and toll receipts on the Dulles Toll Road, for example, which are substantially ahead of projections.

JONATHAN L. GIFFORD Assistant Professor Department of Public Affairs Research Fellow, Transportation Center George Mason University Fairfax