Taxi operators have sued the city over new rules requiring all yellow cabs to go green, saying safety will be jeopardized because cars operating on a mix of gasoline and electric power weren't designed for commercial use.

The lawsuit was filed Monday in U.S. District Court in Manhattan, weeks before an Oct. 1 deadline requiring new cabs to get 25 miles per gallon. It asked a federal judge to strike down the city requirement.

It claims that fuel-efficient vehicles were not built to withstand the pounding that city taxi cabs endure or to be operated as part of commercial fleets.

City law department spokeswoman Kate O'Brien Ahlers said the city hadn't seen the legal papers but expected to consider all its legal actions once it did.

The lawsuit was filed by the Metropolitan Taxicab Board of Trade, a trade association claiming to represent a quarter of the city's 13,000 cabs. Other plaintiffs include a garage that services taxis and a leasing company.

The lawsuit based its arguments in part on a report by an automotive engineer that concluded hybrid vehicles were unsafe as taxis and could not handle the 24-hour operation required on city streets.

The report concluded that some air bags in hybrids might not deploy properly once the cars are outfitted with partitions between seats meant to prevent drivers from being assaulted, robbed or killed.

The report's author, automotive engineer C. Bruce Gambardella, said in a release that the city had an obligation to crash test the modified vehicles or require carmakers to do so before adding them to the fleet.

"It is completely unknown whether these modified cars would pass federal crash tests," he said. "No automaker would put such an inadequately tested vehicle on the road, nor should the public or any federal regulatory agency stand for it."

Gambardella was planning to testify Wednesday at a City Council hearing on the safety of green taxis.