Despite the pollution, congestion and frustration of driving to work on Washington's clogged highways, research suggests that the availability and cost of parking are the single most critical factors in people's decision whether to abandon their cars in favor of mass transit.

Unfortunately, the federal government here subsidizes those who drive or car pool, which, in effect, discourages its employees from taking mass transit. The result? A demand for more highway construction -- and more funding -- with all the attendant environmental and energy impacts.

As this region's largest employer, the federal government could set an example for private industry and local governments across the United States by showing how to maximize the people-carrying capacity of our infrastructure. By acting to manage the cost and availability of parking for employees, it could guarantee that more commuters use some form of public transportation -- including car and van pools.

The usual course of action for the federal government today is to subsidize parking for a few headquarters employees. This subsidy is perceived as a "perk" by the employees who receive it. But all federal employees could share in a "perk" if a program called Consumer Choice, developed at the Urban Mass Transportation Administration, was instituted.

The Consumer Choice program would give employees transportation subsidies that they can put toward the transportation option that serves them best. Money would be placed into a transportation fund to be apportioned equally among all employees. Vouchers would then be issued that could subsidize the cost of either parking or transit fares.

Those who chose to drive alone still could do so -- but they would pay the difference between the value of the voucher and the market-rate cost of parking.

Employees who chose to car or van pool would combine subsidies to cover parking fees. Those that collected vouchers in excess of the cost of parking could exchange unused vouchers for cash to help defray operating costs.

Those who chose public transportation would use their vouchers to defray the cost of transit fares. And those federal employees who resided in a locality offering a benefit such as Montgomery County's Fare Share program could use the voucher to participate in that program and thus collect a double subsidy.

The "Consumer Choice" approach would be an attractive urban development tool, because it would reduce congestion and the need for parking in the central business district without limiting the parking required for healthy economic activity. It makes the most sense for places of employment located in cities that have good public transit options and a ready market for government owned or leased parking.

Obviously, many details need to be worked out before the Consumer Choice approach could be implemented.

But with the Bush administration's commitment to finish 103 miles of Metrorail and the daily frustration of thousands of federal employees who commute to work, there is ample justification for the Office of Personnel Management and the General Services Administration to consider a demonstration of the Consumer Choice idea.

-- Alfred A. DelliBovi is undersecretary of Housing and Urban Development and was administrator of the Urban Mass Transit Administration.