SAN FRANCISCO City leaders here are considering establishing a traffic congestion fee in certain parts of San Francisco during rush hour.

Saying such a fee would fight gridlock and reduce smog and global-warming gases, officials want San Francisco to become the first city in the nation to impose congestion-management fees during rush hour to drive into -- and possibly out of -- the busiest downtown areas.

Fees from $1 to $4 are being examined in an 18-month study of congestion pricing by the San Francisco County Transportation Authority, an agency governed by the San Francisco Board of Supervisors. The money would be invested in public transit and other congestion-reducing measures.

"We're trying to manage a scarce resource, our roads," said Tilly Chang, the transportation authority's deputy director for planning. "There are power and gas rates that put a premium price on use during peak demand. Why not roads, too?" she asks.

Congestion fees for drivers have reduced rush-hour traffic in London, Rome, Stockholm and Singapore by 20 to 30 percent, according to an authority report. An effort to adopt such a plan for lower Manhattan in New York failed earlier year. (See May 1 Bus & Motorcoach News.)

The authority has conducted four public meetings on the plan. Initial recommendations are due in the fall, with a decision expected next year by the San Francisco Board of Supervisors.

Under one option, the city would hire a contractor to electronically collect fees in a four-square-mile area that includes the Financial District, Civic Center and the large South of Market neighborhood. Those without an electronic tag would be identified by a license plate photograph and billed.

Under another option, fees would be collected from drivers entering the city during rush hour. The fees would be in addition to bridge tolls.

Planners have yet to pin down details of the plan, including whether the fees would be collected for driving into and out of pay zones in both morning and afternoon rush hours.

Some San Francisco business leaders worry that the congestion fees would hurt local business, discouraging people from traveling into San Francisco.

"We feel drawing an arbitrary line around part of San Francisco to charge a fee doesn't make sense," said Jim Lazarus, a vice president of the San Francisco Chamber of Commerce.