New York's yellow cabs are to become hybrid cars within five years under a scheme to make the city the greenest in the US.
Michael Bloomberg, the city's mayor, announced the shift to hybrid technology - which powers cars using a combination of fuel and electric batteries - in a bid to cut emissions by more than half over the next decade.
Of the 13,000 yellow cabs on New York streets, only 375 are hybrids. Mr Bloomberg said that number would rise to 1,000 by the end of 2008 and a further 20 per cent of the fleet would go hybrid each subsequent year until 2012. The estimated 50,000 other licensed cabs in the city will not as yet be required to make the shift.
Mr Bloomberg, a potential presidential candidate, said the government had failed to act on fuel efficiency.
"What we are trying to do is make the world a better place without waiting for Washington," he said. "If government does it then private companies realise it is in their best interest as well."
Mr Bloomberg plans to make New York more sustainable by 2030, reducing its greenhouse gas emissions by 30 per cent between now and then.
He has already said that Manhattan will adopt a trial version of congestion charges for cars and trucks, modelled on London's pioneering scheme.
New York will not be the first city to adopt greener taxis - Tokyo already has an "eco-taxi" fleet, as does Vancouver. However, New York says its scheme is the largest in the world.
The city estimates that the increased fuel efficiency of the cars, at 30 miles per gallon as opposed to the current vehicles which run at 14mpg, will save the average taxi operator $10,000 per year. Average US cars run at 24 mpg. Most of the city's yellow taxis are Ford Crown Victorias, which cost $23,000 plus around $2,000 of modifications to turn them into cabs.
Hybrid models tested in the city's fleet over the past 18 months can come in at much higher prices. The Toyota Prius retails from $22,175, the Toyota Highlander Hybrid sells for $32,490 and the Lexus RX 400h costs from $41,180.
The idea seems to have gained support among some of the city's cab drivers:
"Everybody likes it," said Mohammed Babar, a cabbie for about 18 months.
"The hybrid is low-fuel, so everybody's saying 'After this car, maybe I'll go hybrid'."
The New York Taxi Workers' alliance, however, said the cost of the new cabs would affect both drivers' and customers' pockets.