Watch out what you wish for.

The Philadelphia Parking Authority has approved a temporary $1 surcharge on all taxicab rides in Philadelphia, starting at midnight tonight.

The Unified Taxi Workers Alliance of PA had requested the surcharge because of rising gas prices, but some drivers worry that the extra cost will discourage business during the summer.

Cab drivers, who make less than the $7.25 minimum wage, spend an average of $20 per shift on fuel, said union president Ronald Blount. If the surcharge stays in place, it could save an extra $6,000 annually, he said.

Michelle Niv, whose family owns Germantown Cab Co., said that although the extra dollar will help drivers feed their families, it could hurt business. Most Philadelphians walk during warm weather instead of taking taxis, she said, and the added cost could further discourage customers.

Philadelphia's 5,000 cab drivers held out as long as possible, but gas prices are too high to pay out-of-pocket, Blount said. "Most customers already give us extra tip, so I don't think there will be a huge decline in ridership," he said.

The surcharge will remain in place for at least 90 days, even if fuel prices drop, and until the average price is below $3.75 a gallon for 10 days straight, according to the parking authority.

Instituting the surcharge now is a "double-edged sword," said James Ney, the parking authority's taxicab and limousine division director, who added that the authority waited longer this year than in the past to approve it. In 2008, the last time the authority approved a surcharge, riders were charged an extra 50 cents. In the slow summer months, Ney said, "riders are not going to be there anyway, but drivers hope to recoup some of what they're paying in fuel."

Not every Philadelphia cab customer is discouraged by the fare hike. "If I need [a taxi], I'll take it anyway," said Angel Zamary, who was waiting for a private ride at 30th Street Station. "People will probably complain, but it won't be a big deal."

Maura McDermott, walking in Center City, agreed, saying that she takes cabs every weekend: "We all go out and drink so we need a cab. I'll continue taking them."