Low emission buses in London

[2] Transport for London (TfL) note that the bus fleet has lower carbon dioxide emissions per passenger kilometre of than other major cities such as New York, Paris and Vancouver.

Converting London's entire bus fleet to hybrid vehicles would reduce CO2 emissions by around 200,000 tonnes per year.

[13][14][15] In 2000, three DAF SB220 East Lancs Myllennium buses powered by liquefied petroleum gas were used to transport visitors to the Millennium Dome.

[19] In January 2004, three hydrogen fuel cell powered buses were introduced on route 25 on a two-year trial.

[24] The single decker buses were unveiled by Mayor of London, Ken Livingstone on 7 February 2006, with the intention of starting operation on the following day.

The bus, which cost £285,000 and was constructed by Wrightbus, was the first hybrid double-decker in the world, and was painted in red and green to symbolise the environmental benefits.

A further eighteen entered service in July 2009, when six Volvo B5L double-deckers joined the existing vehicles on route 141.

This was achieved in July 2012, when an Alexander Dennis Enviro400 double-decker of Abellio London became the 300th hybrid in use when it entered service on route 211.

Although it is intended that the units are to operate in "pure electric" mode, a standard diesel engine is also carried.

[34] In the 2010s, bus operators retrofitted older buses to improve fuel economy, reduce air pollution and meet emission standards.

[4][37] A Kinetic energy recovery system using a carbon fibre flywheel, originally developed for the Williams Formula One racing team, has been modified for retrofitting to existing double-decker buses.

500 buses from the Go-Ahead Group will be fitted with this technology from 2014 to 2016, anticipated to improve fuel efficiency by approximately 20%.

[42] In October 2022, rapid charging using a pantograph was introduced for battery electric buses on route 132, testing the use of this technology in London.

[56] In November 2023, tour bus operator Tootbus London announced they would be retrofitting their buses with electric drivetrains from Magtec, making them zero-emission.

[60] Bus operator Arriva London reported that they are investing £730 million in upgrading and electrifying their garages.

[61] Bloomberg reported challenges regarding the electrification of bus depots, such as competing demands for land (new housing and industry), as well as the cost and delays of connecting to high voltage electricity.

In June 2021, the world's first hydrogen fuel cell double-decker bus – the Wright StreetDeck Hydroliner – entered service on route 7.

[68] Research by operator Go-Ahead showed that people would be more likely to travel by bus if they knew the journey would be zero emission.