It's been talked up before, but the transport ministry in Japan is currently seriously considering forcing car manufacturers of near-silent hybrid vehicles to add sound to their motors.

"We have received opinions from automobile users and visually-impaired people that they feel hybrid vehicles are dangerous", a transport ministry official told the AP.

"Blind people depend on sounds when they walk, but there are no engine sounds from hybrid vehicles when running at low speed".

A panel of experts including the police and groups representing the visually-impaired have met to discuss the matter and, after the first meeting, decided that a "sound-making function" should be introduced.

This would mean hybrid cars, such as the Toyota Prius, would be manufactured to create noise when in electric mode.