"Green" speed bumps that will generate electricity as cars drive over them are to be introduced on Britain's roads. The hi-tech "sleeping policemen" will power street lights, traffic lights and road signs in a pilot scheme in London that could be rolled out nationwide.

Speed bumps have long been the bane of motorists' lives, but these will capture the kinetic energy of vehicles.

Peter Hughes, the designer behind the idea, said: "They are speed bumps, but they are not like conventional speed bumps. They don't damage your car or waste petrol when you drive over them - and they have the added advantage that they produce energy free of charge." An engineer who formerly advised the United Nations on renewable energy sources, Hughes added: "If it [the energy] wasn't harnessed by the speed bumps, it would go to waste."

The ramps - which cost between £20,000 and £55,000, depending on size - consist of a series of panels set in a pad virtually flush to the road. As the traffic passes over it, the panels go up and down, setting a cog in motion under the road. This then turns a motor, which produces mechanical energy. A steady stream of traffic passing over the bump can generate 10-36kW of power.

The bumps can each produce between £1 and £3.60 of energy an hour for up to 16 hours a day, or between £5,840 and £21,024 a year. Energy not used immediately can be stored or fed into the national grid.

"With a steady flow of traffic, four of the ramps used as speed bumps would be enough to power all the street lights, traffic lights and road signs for a mile-long stretch of street. The ramp is silent, comfortable and safe for vehicles. It is not only green energy; it is free energy, once you have paid for the capital cost of the equipment," said Hughes. "The full potential of this is absolutely enormous." Hughes claims that 10 ramps could generate the same power as one wind turbine.

The "electro-kinetic road ramp" system can either be raised to act as a speed bump or laid flat, so that drivers don't realise they are passing over it.

A spokesman for Ealing council in west London confirmed that £150,000 of funding had been secured for the scheme: "The money is there for the scheme in 2009-10," she said. "The details - how many speed bumps there will be and where they will be - still needs to be finalised. It is an innovative idea. We are excited to be part of it."

Hughes said he had been in talks with more than 200 councils interested in introducing the system, as well supermarket chain Morrisons about a flat version of the ramp at its depot in Sittingbourne, Kent.

Speed humps were introduced in the UK in 1981. There are an estimated 30,000 in London and at least that number in the rest of the country. Conventional speed humps cost about £2,000 each.

A nightclub opened in Rotterdam in the Netherlands last year that is run partly on energy generated by people dancing. Last year, it was also reported that pedestrians' footsteps could be used to power lighting at shopping centres.