This week, San Francisco celebrated becoming the “Greenest Taxi City in America,” having met mandates it enacted in 2008 to slash fuel consumption and greenhouse gas emissions by 20 percent – a target based on 1990 levels intended to be met this year.

At a gathering attended by California Lt. Gov. Gavin Newsom and San Francisco Mayor Ed Lee, among others, former city Taxi Commission President Paul Gillespie noted the city’s level of commitment.

“Cutting global carbon dioxide emissions is one of the most crucial issues of our time,” Gillespie said, “and the San Francisco taxi experience has shown that taking aggressive, collaborative action at the local level can be both profitable and effective.”

Officials observed that when goals were set, people had said they did not know they could be accomplished – but met them, they have.

Since 2008, San Francisco taxis are said to have consumed 2.9 million fewer gallons annually, while spewing 35,000 fewer tons of greenhouse gas per year.

According to Ford, these levels were reached in part with Ford-brand vehicles, of which 67 percent of San Francisco’s taxi fleet is comprised.

A portion of San Francisco’s fleet relies on compressed natural gas (CNG) or liquefied propane gas (LPG), but a number of taxis are the imported-from-Europe Transit Connect which is fueled by regular gasoline or natural gas.

Ford noted that CNG-powered versions “are available and soon will hit the streets of San Francisco,” and the standard gasoline Transit Connect uses a 2.0-liter I-4 engine that gets 22 mpg in the city and 27 mpg on the highway – an estimated 30-percent improvement in fuel economy compared with traditional Crown Victorias, for example.

The new Euro vans have thus relegated the once-ubiquitous Crown Vic to the endangered species list, and Ford says even cleaner CNG-powered Transit Connects are on their way and already in use in other regions, including Los Angeles, Chicago, Las Vegas and St. Louis.

As are other automakers, Ford is touting where possible the advantages of natural gas which has previously been in use in other taxis including Crown Victorias.

The gasoline-powered Transit Connects get decent mileage, the company says, but CNG versions put out fewer emissions and save money because the energy equivalent of a gallon of CNG costs roughly half that of a gallon of regular gasoline.

Ford also took the opportunity to pitch its improving hybrid technology. The outgoing Escape Hybrid is being replaced by the incoming CNG Transit Connect, it said, but also available is the new Fusion Hybrid, which Ford says should deliver 6 more miles per gallon than the existing Fusion Hybrid.

These announcements come also as Ford, like many other automakers, hedges its green car bets between electrified vehicles and vehicles that can make use of natural gas.

The “all of the above” approach is in fact a shakeout process and in lockstep with not just city policymakers, but also those at the state and federal levels hoping to wean from petroleum dependence.

The message is essentially that there’s more than one way to skin a cat – CNG, LPG, hybrid, all-electric, mild hybrid, diesel – and, one could infer, may the best technology win.

Do you have an opinion on which technology makes best sense for such regional fleets?