The sight of Lincoln Town Cars idling at the curbside, will soon begin disappearing from

streets, as city fuel economy rules, written to curb the thirst of black cars, will steadily sideline the big V-8 powered sedans, according to the New York Times.

The rules particularly threaten the future of the Lincoln Town Car. Under a plan introduced by Mayor Michael R. Bloomberg last winter, new black cars that enter service beginning Jan. 1 must carry a fuel economy rating of at least 25 miles a gallon in the Environmental Protection Agency’s city test cycle; the requirement steps up to 30 mpg a year later. A 25-mpg rule took effect for

’s 13,000 yellow taxis in October.

According to the city, the black cars, taxis and an additional 25,000 local car service vehicles produce 1 percent of the city’s total carbon dioxide emissions, and 4 percent of its transportation emissions. Doubling the mileage of that entire fleet, the goal by 2017, would cut the emissions by half.

The only problem is that no new full-size sedan comes close to 25 mpg, let alone 30 mpg, in city driving. The Lexus LS 600h L, the only large hybrid luxury sedan, is rated at just 20 mpg in the city. Its $100,000-plus price makes it way out of reach for independent drivers who are used to paying $15,000 to $25,000 for a used Town Car or $40,000 for a new one.

Still, with fleet operators and drivers being hammered by wild swings in fuel prices, the mileage rules provide a powerful incentive for switching to smaller hybrid sedans and crossovers that comply with the new regulations.

The possibilities include Ford’s Escape and Mercury Mariner hybrids, crossovers that are rated at 34 mpg in town. The Mariner costs about $31,000 with a livery package that includes black-leather upholstery and a GPS navigation system. The Toyota Highlander Hybrid utility wagon and the Lexus RX 400h can achieve 27 mpg in the city and would cost drivers $40,000 to $50,000.

Among midsize sedans, the Toyota Camry and Nissan Altima hybrids achieve 33- and 35-mpg in city driving, and each costs about $30,000 with options. The Toyota Prius achieves at 45 mpg in the city, though some black-car drivers say the Prius is too small and bare-bones to step in for a Town Car.

John Acierno, president of the city’s largest black-car company, Executive Transportation Group has already switched about 10 percent of his 1,750-car fleet to hybrids. With Town Cars achieving only 12 mpg in real-world use, hybrid adopters are saving from $125 to $175 a week in fuel, Acierno said, enough to offset the higher purchase price of the hybrids.

For operators who are not ready to get rid of their

, the city plan includes a phase-in retirement period. Essentially, six-year-old Town Cars will be steadily removed from service, with virtually the entire fleet converted to the 30-mpg. standard after 2013. Operators who license a new 2009 Town Car before Jan. 1 will be able to operate it the longest, for five years, before it is forced to retire.

Ford has pledged to continue building Town Cars through 2011 at its plant in

.