On average the new buses will require 28 litres of fuel per 100 kilometres.
It will carry 87 people - 62 sitting and 25 standing - about the same as a conventional double-decker but almost half the number of a bendy bus.
Wheelchair users and people with pushchairs will be able to board the bus using the middle door, which will fold out a ramp like conventional buses.
The first prototype will be delivered late next year, with the new buses entering service from early 2012.
When he took office in 2008, Mr Johnson vowed to bring back a 'greener' version of the Routemaster, which was first introduced in London in the mid-1950s.
The Routemaster was withdrawn from regular service in December 2005 by Mr Johnson's predecessor Ken Livingstone because they were inaccessible to wheelchairs and pushchairs.
Some classic Routemasters still run on a limited basis on two tourist routes in London where they complement the full-time service.
Mr Johnson said today: 'This iconic new part of our transport system is not only beautiful, but also has a green heart beating beneath its stylish, swooshing exterior.
'It will cut emissions, and give Londoners a bus they can be proud of, complete with cutting edge design, and the freedom of an open platform.
'I expect to eventually have hundreds of these on London's roads, and for cities around the globe to be beside themselves with envy for our stunning red emblem of 21st century London.'
What a waste of money. 10 million could have gone towards cheaper fares 5% increase while Boris wastes money on a vanity bus. Vote for Ken
colcfc123 2 months ago