The lawsuit raises other safety concerns as well, charging that the partitions that owners must install between the front and rear seats of the taxis may prevent side-curtain airbags in the cars from opening properly.  And it warns that because there is less room in the rear seat than in the Crown Victoria, passengers could be injured, hitting their faces on the partition, during a crash.  A spokeswoman for the city legal department declined to comment on the suit, saying that city lawyers had not yet received the legal papers.  Matthew Daus, the Taxi and Limousine commissioner, rejected the industry’s safety concerns.  “These cars and the partitions that are in them are 100 percent safe,” Mr. Daus said.  He said that partitions had been redesigned to make sure they did not block the side airbags. And he said that seat belts and shoulder harnesses would keep passengers from hitting the partition in an accident even in the more cramped rear seats of the hybrid cabs.  Allan J. Fromberg, a spokesman for the commission, said that many drivers had already switched to hybrid vehicles voluntarily and that some medallions required cabs to be hybrids. Indeed, Mr. Fromberg said on Tuesday, of the 13,237 yellow cabs on the road, 1,400 were hybrids.  Under the city rules disputed in the lawsuit, the 25 mile per gallon requirement would be raised to 30 miles per gallon for new vehicles beginning in October 2009.  A version of this article appears in print on , on Page B2 of the New York edition with the headline: Taxi Group Sues to Block New Mileage Rule for Cabs. Order Reprints| Today's Paper|Subscribe
A city rule effectively requires most new taxis to be hybrid vehicles, a key part of the mayor’s push to cut pollution and make city policies more sensitive to environmental concerns.