And drivers will feel the pain in their pocketbooks.

To reduce traffic caused by drivers circling the block to find parking, cities are testing new technology to direct people to open spots and experimenting with a concept known as congestion pricing. The strategy calls for hiking meter rates during peak hours when parking is scarce and lowering the cost when spaces are plentiful.

Transportation officials believe the higher prices will discourage drivers from staying put for too long. That, in turn, could increase the turnover of spaces and reduce carbon emissions caused by cars on the prowl for curbside spots.

They suggest the extra money from the meters could be used to improve mass transit.

New York and Washington, D.C., are testing a form of congestion pricing for parking. Chicago, Los Angeles and San Francisco aren't far behind.

"This new approach holds the promise of a simpler, more elegant solution to congestion," said Jay Primus, manager of San Francisco's parking program.

Los Angeles has already raised rates for the first time in nearly two decades, now charging as much as $4 an hour for curbside parking in parts of downtown. Later this year, the city plans to adjust rates at about 15,000 parking meters in the downtown area based on demand.

Some motorists are balking at the plan.

"I think the rate is ridiculous as it is," Shawn Tillman said as he reloaded a meter in Little Tokyo on a recent weekday. He complained that traffic hasn't improved since the rates there jumped from $1 to $2 an hour.

The pricing strategy is based on research by Donald Shoup, a professor of urban planning at the University of California, Los Angeles whose 2005 book, "The High Cost of Parking," has influenced parking policy in many cities.

Shoup said curbside parking is largely underpriced compared to the cost of parking in private lots and garages, a situation that encourages people to cruise for open spots on the street and causes an astonishing amount of congestion.

In an observation of traffic near the UCLA campus, Shoup found that motorists spent an average of 3.3 minutes driving about half a mile in search of a parking space. Over a year, vehicles traveled a total of 950,000 miles - the equivalent of 38 trips around the Earth - to find parking in the 15-block area, he said.

Shoup said the solution lies in looking at demand for parking and setting the right cost at the right time.

So what's the right price?

"It's the Goldilocks principle; it shouldn't be too high or too low," Shoup said. "It's just right when there's one to two vacant spaces on every block."

Congestion pricing has been employed on several U.S. freeways where motorists looking for a faster commute can enter toll lanes. The toll varies, depending on the amount of traffic.

San Francisco is considering what would be a first-in-the-nation plan to charge drivers a toll for driving in and out of the downtown area during the most congested hours. The city will soon begin an ambitious pilot program involving 6,000 multi-space street meters and 11,500 city-owned garage spaces.

The $23 million project, called SFpark, will involve the installation of ground sensors to detect when a space is vacant. The data will then be sent to a computer database that will alert drivers to available spots via displays on electronic street signs or by maps on the Internet and handheld devices.

The high-tech meters, which resemble ATM machines, accept payments by coin, debit, credit card or over the phone to a meter operator. Users can even receive text messages warning them when their time is almost up and pay for longer stays with their cell phones.

The real-time data also will help the San Francisco Municipal Transportation Agency determine demand then hone in on the right price. The city currently charges $3 an hour to park at a metered spot in the downtown core.

"We'll change it slowly and gradually so people can learn the prices and over time adjust their travel behavior," Primus said.

This article appeared on page A - 13 of the San Francisco Chronicle