Mayor Michael Bloomberg's plan to make every cab in the Big Apple a hybrid or clean diesel by 2012 has hit a big pothole with a judge's ruling that only the feds can set fuel efficiency rules.

U.S. District Judge Paul Crotty granted a temporary injunction halting the plan after ruling the Metropolitan Taxicab Board of Trade had "demonstrated a likelihood of success" in having it tossed out. The ruling could have implications beyond New York because Bloomberg's proposal was considered a model for other cities. Crotty said fuel efficiency standards are exclusively a federal matter, mirroring the view of the Environmental Protection Agency director who made the same argument last year when he rejected California's petition to limit vehicle emissions.

Bloomberg hasn't said whether he'll appeal the decision, but he isn't backing down in his campaign to clean up the city's cabs. “Greening the taxi fleet is a major priority and we are going to use every mechanism at our disposal to make New York a cleaner, healthier city,” he said in a statement.

The mayor's plan to require every new taxi to get 30 mpg - a target met only by hybrids and clean diesels - is an example of the pragmatic, if limited and imperfect, action that's needed if we're as worried about climate change and energy independence as we pretend to be when we see Al Gore or T. Boone Pickens on TV.

The taxi industry isn’t limiting its fight to the courts. The Taxicab Board, an association representing about 25 percent of the city's cabs, has launched a PR offensive on the “hazards” of hybrids taxis. The statement it issued last month — “Hybrid Escape Taxis Getting

Totaled, Rolling Over, Causing Injury and Damage on New York City

Streets” — shows how far it will sink to avoid the admittedly significant costs of retooling entire fleets. Granted, the venerable Crown Victoria has a five-star safety rating, but the three-stars the National Highway

Safety Administration gave the Ford Escape Hybrid hardly makes it a deathtrap.

Despite the Taxicab Board's best (worst?) efforts, Bloomberg has had some success using incentives, including new taxi medallions reserved exclusively for hybrids, to green the fleet. Some 1,500 of New York City’s 13,237 taxicabs are hybrids. The gas-electric vehicles are catching on in other cities, including San Francisco, where Ford says some Escape Hybrid cabs have racked up 100,000 miles, and Boston, where cab drivers are wicked mad about the city's plan to convert the entire fleet by 2015.

But the decision Crotty issued last week is a stark reminder of the bureaucratic and regulatory barriers that must be cleared before we begin to put a serious dent in carbon emissions.

Photo by Flickr user Iceman75.