NEW YORK -- The city's fleet of yellow cabs will go entirely hybrid within five years, and all its vehicles for hire will have to meet new emissions and mileage standards by next year, Mayor Michael Bloomberg announced Tuesday.

Today, there are just 375 fuel-efficient hybrid vehicles among the 13,000 taxis rolling on city streets. That number will increase to 1,000 by October 2008 and will grow by about 20 percent each year until 2012, when every yellow cab will be a hybrid.

Hybrid vehicles run on a combination of gasoline and electricity, emitting less exhaust and achieving higher gas mileage per gallon. Changing over the fleet is part of Bloomberg's wider sustainability plan for the city, which includes the goal of a 30 percent reduction in carbon emissions by 2030.

"There's an awful lot of taxicabs on the streets of New York City obviously, so it makes a real big difference," Bloomberg said. "These cars just sit there in traffic sometimes, belching fumes; this does a lot less. It's a lot better for all of us."

The hybrids that have been successfully tested in the city's taxi fleet over the past 18 months include the Toyota Prius, the Toyota Highlander Hybrid, the Lexus RX 400h and the Ford Escape.

Bloomberg made the announcement on NBC's "Today" show. In addition, Yahoo Inc. said it would donate 10 hybrid Ford Escape taxis, which get 36 miles per gallon.

The standard yellow cab vehicle is the Ford Crown Victoria, which gets 14 miles per gallon.

Besides making the yellow cab brigade entirely green within five years, the city will require all new vehicles entering the fleet after October 2008 to achieve a minimum of 25 miles per gallon. A year later, all new vehicles must get 30 miles per gallon and must be hybrid.

City officials said the new standards, when fully implemented, are expected to reduce carbon emissions by more than 200,000 tons per year.

Hybrid vehicles are typically more expensive, but the city said the increase in fuel efficiency will save taxi operators more than $10,000 per year.