The BBC reports on a problem that anyone driving electric vehicles knows well-people do not hear you when you approach. So while having a quiet car is good in many ways, for people who are sight impaired or just not paying attention having an acoustical cue that an electric or hybrid vehicle is approaching is a good thing.

The US National Highway Traffic Safety Administration demands that the cars make a noise when travelling either forwards or backwards at speeds of less than 30km/h (19mph). The regulation covers vehicles with four wheels that weigh less than 10,000 pounds (4.5 tonnes).

The safety specification requires car makers to use a two-tone signal similar to that currently emitted by heavy vehicles when they are reversing. Estimates of injuries that could be prevented by electric and hybrid  vehicle noise are about 2,400 annually in the United States. These new systems have a name -they are Vehicle Alerting Systems (AVAS), or “additional safety cues” for pedestrians.