SAN FRANCISCO  In a city known for its pricey property, and terrible parking, some of the most valuable real estate may soon be curbside.

Under a trial plan passed Tuesday by the board of the San Francisco Municipal Transportation Agency, 6,000 of the city’s precious parking spots will be priced on a sliding scale depending on how popular they are. And while the worst locales will go cheaply  as little as a quarter  a handful of premium parking spots will be worth $18 an hour, or nearly a pound of quarters.

Other cities have dabbled in such pricing, but Nathaniel P. Ford Sr., executive director of the transportation agency, said San Francisco’s plan  due to start in the spring with the aid of new meters, sensors and $18.4 million in federal financing  would place the city at the forefront of parking technology. Mr. Ford cited the various benefits it would reap, including reducing congestion and carbon emissions from circling cars and ensuring pedestrians are not sideswiped by parking-obsessed drivers.

“It’s an exciting time,” said Mr. Ford, who also pointed to advances in payment technology, including the ability to buy parking time with a cellphone.