Dec. 19 (Bloomberg) -- London Mayor Boris Johnson unveiled two new designs for the city’s iconic Routemaster double-decker buses and vowed to put a 21st century version of the vehicle on the road by 2011.

The city sold off its original fleet of red Routemasters three years ago after almost 50 years of service. They were replaced with new buses including the 18-meter (59-foot) single- deck “bendy” model.

Johnson, a former Conservative member of Parliament who was elected in May, promised during the campaign to scrap the “bendy” and bring back the Routemaster. One critic called the plan “bonkers,” though it proved popular with voters in a city that operates one of the world’s busiest bus networks.

“Let’s seize this opportunity to design a new Routemaster that will do this city proud,” Johnson said at a news conference today to show the winning entries in a bus design contest held by the city.

The winning plans came from a venture between U.K.-based sports-car maker Aston Martin and architects Foster and Partners; and from Capoco Design Ltd., an automotive studio based in Salisbury, England.

The city will pass the proposals to bus makers for further development and will seek bids next year for the contract to build the vehicle, said Peter Hendy, London’s transportation commissioner.

The new model will use environmentally friendly technology such as diesel-electric power and lightweight metal bodies. Both designs, like the original Routemaster, have an open rear platform to allow passengers to jump on and off and would use conductors to collect tickets, Hendy said.

Hendy and Johnson declined to provide figures on what the project will cost or the price of the buses compared with current models.

“It’s bonkers,” Christian Wolmar, author of “Subterranean Railway,” a book about the London Underground, said in a telephone interview. “It’s going to cost a fortune.”

Labour Party members of the city’s legislative assembly said in a statement that the new bus project would be a waste of public money.

London’s 8,000 buses carry 1.8 billion passengers annually. The fleet includes Volvo AB’s modern double-deckers and the “bendy” buses made Daimler AG.

The original Routemaster was introduced to the capital’s roads in 1956 based on a London Transport department design. They had innovations such as power-assisted steering and an automatic transmission. From 1958 to 1968, 2,876 of the buses were built, according to the Routemaster Association Web site.

Mayor Ken Livingstone removed them in 2005, saying they were too costly to run and difficult for elderly and disabled riders to use. He was defeated by Johnson in the May election.

The city operates a few reconditioned Routemasters on tourist routes.

To contact the reporter on this story: Brian Lysaght in London at blysaght@bloomberg.net.

Last Updated: December 19, 2008 09:25 EST