New Yorkers are facing the second day of a 48-hour strike by taxi drivers protesting over the introduction of new technology in their cabs.
A cab driver heckles taxis arriving at Pennsylvania Station
Authorities want new credit card systems and satellite tracking, which they say will help with lost luggage.
Some drivers say the devices could be used to track their movements.
Organisers said the first day was a "resounding success" but Mayor Michael Bloomberg said 75% of the fleet cabs were working.
The strike comes during New York Fashion Week and the US Open tennis championship.
The city has about 44,000 licensed drivers and 13,000 registered yellow cabs.
At inspections from 1 October, the cabs are required to have GPS satellite tracking systems and video screens to allow passengers to see their location, plus credit card payment facilities.
The City Taxi & Limousine Commission said the credit card system could create bigger fares and the GPS would help with lost luggage.
Strike organisers, the New York Taxi Workers Alliance, fear the GPS will spy on drivers, whom it says will also have to pay credit card transaction fees.
The alliance's leader, Bhairavi Desai, told AFP news agency: "Taxi drivers sometimes use the cars in their private time. Why should they tell the [commission] where they are going on a Sunday with their family? This is an invasion of privacy."
The impact of the strike on Wednesday was disputed.
Mr Desai said only 10% of the 13,000 registered cabs were working.
But city officials put the number of taxis working at 75-80%.
Mayor Bloomberg said: "The city has not come to a stop and people are getting where they need to go."
The city allowed drivers who were working to offer group rides to separate passengers and let them pay flat rates rather than metered fares.
British businessman Mark Yaffe, who arrived in New York on Wednesday, told the BBC News website: "People are spending a lot longer trying to hail what few cabs there are.
"If one stops for you, it's likely to already have two or three people in it. They're charging a flat rate of $10 (£4.95) to anywhere in Manhattan, but if you find a cab, you're happy to pay it."
Some reports said there were more cabs about on Thursday.
Michael Woloz, of the Metropolitan Taxicab Board of Trade, which represents 3,200 taxis, told the New York Post: "The drivers were hearing how much everyone was making out there and decided to go to work."
The paper said some drivers had quadrupled their takings.
Driver Taj Dass told the Post: "I did not work yesterday, but how can I afford to stay out a second day?"