Roughly a year ago, New York City Mayor Michael Bloomberg announced a bold new plan to replace all of New York’s 13,000 taxis with hybrids within a few years. A year later, the most prevalent yellow cab in the city is still the Crown Victoria—which only gets around 13 miles to the gallon—but the number of hybrids roaming the streets has nearly tripled from 375 to 1,020. Thanks to a Taxi and Limousine Commission regulation mandating that all new cabs get 30 miles a gallon, the last gas-guzzling Crown Victorias are expected to disappear by 2012.

Although other cities have experimented with adding hybrids to their commercial transportation fleets, Mayor Bloomberg’s plan is by far the most ambitious, and is one of the cornerstones of his “PlaNYC,” which seeks to reduce New York’s carbon emissions by 30 percent by 2030. Upgrading the cabs is expected should be roughly equivalent to taking 32,000 non-commercial cars off the road. New York City’s cabbies have been largely receptive to the change because of the major savings hybrids provide in fuel costs.

Boston, which began its push to bring hybrids into its cab fleets a year and a half ago, has had considerably less success. According to a recent article in the Boston Globe, only 32 of the 1,825 cabs in Boston are hybrids. While the city has attempted to provide incentives to drivers and fleet owners, it has failed thus far to enact any mandates that might ensure a quicker transition to more fuel-efficient taxis.