With major automobile companies in United States going full throttle to launch a slew of electric cars in coming days, lawmakers are concerned about the new developments and trying to find a solution.

In a recent development, the US Congress has banned ''silent'' vehicles to improve safety for pedestrians, cyclists and other road users.

Traffic authorities have been given 18 months to set a minimum volume for extremely silent cars. The law stipulates warning signals when a vehicle travels at silent low speeds.

Associations for the blind have welcomed the regulation which still has to be signed into law by US President Barack Obama.

Several electric car makers however offer noise options for buyers that range from the whoosh of the Starship Enterprise to a sports-car like roar akin to a Ferrari or Lamborghini.

Few months ago researchers at Warwick University's WMG (formerly Warwick Manufacturing Group) had built electric van called ELVIN (Electric Vehicle with Interactive Noise) to find out what noises alert pedestrians efficiently and yet do not annoy them.

Electric Vehicles are very quiet externally and internally, which makes them a potential low-speed safety risk to pedestrians. Sound not only alerts people to the presence and direction of a vehicle, it also indicates the type of vehicle -- for instance a bus -- and whether it is stopping or accelerating, the lead researcher on the project, Professor Paul Jennings from WMG at the University of Warwick said on the university website.