The diesel engines used over several generations of taxi have been picked for their durability--racking up many hundreds of thousands of miles--rather than their cleanliness, and along with other outdated diesels have contributed to much of London's inner-city pollution.
A greener solution is looking ever more important, which is where the range-extended electric Ecotive Metrocab comes in.
Unveiled just before Christmas with London mayor Boris Johnson in attendance, the Metrocab is an all-electric taxi designed by Ecotive and Frazer-Nash.
According to Metrocab chairman Sir Charles Masefield, the vehicle is a "next-generation" London taxi designed to meet the typical duty cycle of a regular London cab, including the longer drives many cabbies make to their first destination.
That's why a range-extended electric drivetrain has been chosen--Sir Masefield says that current charging infrastructure around London makes a pure electric taxi impractical for the full day of driving undertaken by many cab drivers.
Full details aren't yet forthcoming, though the company says the Metrocab is powered by a lithium-ion battery pack and uses an electric motor for each rear wheel. It isn't clear what engine will be used for the range-extended part of the car's drivetrain. The company does suggest economy of more than 62 mpg in use--far better than the 20-25 mpg of current taxis.
Interior space has been prioritized with six passenger seats, and as a purpose-designed London cab it'll also have to meet the 25-foot turning circle requirement of all black cabs--designed to negotiate the tight entrance circle at the Savoy Hotel.
It also features a glass roof like the Nissan "Taxi of Tomorrow" rolling out in New York, while styling is a clear nod towards the existing taxis, themselves modeled on the classic Austin FX4 introduced in 1958.
The Metrocab is the latest in a line of greener transport measures introduced to London over the past decade, aimed at cutting city center pollution. It began under previous Mayor Ken Livingstone with a bicycle-share system--now nicknamed "Boris Bikes" after being rolled out under the current mayor--as well as the "New Bus for London" double-decker bus, which also uses a range-extended electric layout.
Preliminary trials of the cab will begin on London's streets in early 2014.