A group of taxi drivers launched a two-day strike Wednesday, right in the middle of the New York Fashion Week and the U.S. Open tennis tournament, to protest a city plan to require GPS tracking in cabs.

As the morning rush hour got under way, the lines of commuters waiting for taxis outside Pennsylvania Station were longer than usual, but there were still cabs on the streets.

Financial analyst Matt Achilarre said he had waited almost 20 minutes for a taxi there and had no sympathy for the striking drivers.

"It's pointless — they're not making any statements," said Achilarre, 26, who commutes by train from New Jersey. "I applaud the cabbies that are working. They'll get a windfall."

The New York Taxi Workers Alliance called the strike in the nation's largest city to protest new rules requiring all cabs to have global positioning systems and touch-screen monitors that will let passengers pay by credit card. Some cabbies fear the GPS systems could be used to track their movements and that they could get stuck paying hefty fees for credit card processing.

"The overwhelming majority of drivers are against this system, and there are serious setbacks this system is causing drivers," the alliance's executive director, Bhairavi Desai, said Wednesday.

Desai said the drivers' group hoped the strike would persuade city officials to back off the requirement.

It wasn't immediately clear how many of the city's 13,000 taxis would be idled. The alliance claims to represent about one-fifth of the Taxi & Limousine Commission's 44,000 licensed drivers, but its leaders predicted a larger number would join in. However, several other groups that represent thousands of city cab drivers released statements opposing the strike.

Mayor Michael Bloomberg downplayed the likelihood of widespread disruption, but the city still allowed taxis to pick up multiple separate passengers, and the transit system added buses on some airport routes. Normally, taxi drivers are allowed to pick up only one passenger or group of passengers at a time.

The mayor's office had no immediate comment on the situation Wednesday morning. A taxi commission spokesman did not immediately return a message left on his cell phone.

The New York Police Department assigned extra police officers to taxi garages and transportation hubs, and plainclothes officers were to ride in some taxis to guard against reprisals against cabbies who chose not to strike, police Commissioner Raymond Kelly said.

The city's cabs must have the high-tech equipment when they come up for inspection, starting Oct. 1. Taxi officials say eliminating the need for cash could increase ridership and drivers' incomes, and that the GPS technology will be used to give drivers traffic tips and help passengers find lost items.