By George P. Hassett

City officials and owners of Green Cab unveiled the city’s first hybrid taxi this week in Davis Square. Board of Aldermen President Robert C. Trane said the move is part of an initiative to “go green and save green” throughout the city.

“We have the highest asthma rates in the state, we have to do anything we can do to lower our carbon footprint,” he said.

And now, beginning at 4 a.m. Tuesday morning, Somerville residents can call Green Cab and get a hybrid taxi at their door. A hybrid Saturn sedan is the city’s first and, so far only, hybrid taxi on city streets.

Its roots stretch back five years when Green Cab owners started examining the possibility of a hybrid taxi after an MIT student called them with the idea, said Cheryl Horan of Green Cab.

“We’re a willing partner with the city to go green,” she said.

But there are still some questions to be answered about Green Cab’s new green cab. Horan said the hybrid taxi has less leg room in the back seat because of the hybrid battery and it remains to be seen if the new breed of taxi can match the durability of the old ones. Horan said a typical cab lasts about 18 months being driven 24-hours a day. Horan said she hopes the hybrid will last three years but does not know if that will happen. Also, the insurance for the new hybrid costs $4,000 more than for a regular cab, she said.

However, city officials still believe the move could be economically feasible for Green Cab and environmentally helpful for New England’s most densely populated city. “As fuel costs rise, we think the economics will balance out,” Trane said.

Ward 5 Alderman Sean O’Donovan said city leaders wanted to work with private businesses to improve their environmental impact, not pressure them and hurt business.

“You want to be environmentally sound but you don’t want to crush companies economically,” he said.

Somerville’s effort to lead the way in environmental matters has even influenced a leader from another continent. Anthony Raimondi, the mayor of Gaeta, Italy, accompanied Mayor Joseph A. Curtatone to Monday’s unveiling of the new hybrid taxi. Raimondi, who lived on Somerville Avenue until he was 9, said he hopes to learn from the local initiative and bring its lessons back with him to Italy.

‚ÄúPollution is a worldwide problem and we hope to learn from Somerville on how to deal with it,‚Äù he said.