As required by the bipartisan Pedestrian Safety Enhancement Act of 2010, the U.S. Department of Transportation's National Highway Traffic Safety Administration is proposing that hybrid and electric vehicles meet minimum sound standards in order to help make all pedestrians more aware of the approaching vehicles.

"Safety is our highest priority, and this proposal will help keep everyone using our nation's streets and roadways safe, whether they are motorists, bicyclists or pedestrians, and especially the blind and visually impaired," said U.S. Transportation Secretary Ray LaHood.

Electric and hybrid vehicles do not rely on traditional gas or diesel-powered engines at low speeds, making them much quieter and their approach difficult to detect.

The proposed standard, Federal Motor Vehicle Safety Standard No. 141, would fulfill Congress' mandate in the Pedestrian Safety Enhancement Act that hybrid and electric vehicles meet minimum sound requirements so that pedestrians are able to detect the presence, direction and location of these vehicles when they are operating at low speeds.

"Our proposal would allow manufacturers the flexibility to design different sounds for different makes and models while still providing an opportunity for pedestrians, bicyclists and the visually impaired to detect and recognize a vehicle and make a decision about whether it is safe to cross the street," said NHTSA Administrator David Strickland.

The sounds would need to be detectable under a wide range of street noises and other ambient background sounds when the vehicle is traveling under 18 miles per hour. At 18 miles per hour and above, vehicles make sufficient noise to allow pedestrians and bicyclists to detect them without added sound.

Each automaker would have a significant range of choices about the sounds it chooses for its vehicles, but the characteristics of those sounds would need to meet certain minimum requirements. In addition, each vehicle of the same make and model would need to emit the same sound or set of sounds.

NHTSA estimates that if this proposal were implemented there would be 2,800 fewer pedestrian and pedalcyclist injuries over the life of each model year of hybrid cars, trucks and vans and low speed vehicles, as compared to vehicles without sound.

The proposal is now open to public comment for the next 60 days.

According to an article by the Motor & Equipment Manufacturers Association, there are a number of companies that have already begun working on adding technology so as to emit sounds at low speeds. These companies include the Chevrolet Volt, the Nissan Leaf and the Toyota Prius.

The cost of adding the speakers and technology is approximately $30, according to the MEMA article.