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Electric vehicles and hybrids are giving manufacturers a new set of safety challenges.

Because they operate virtually in total silence, pedestrians can be unaware of their presence. This is even worse if the person is partially sighted or blind and rely on a guide dog. In fact, research by the NIHTSA shows there is double the risk of pedestrian accidents in parking areas with EVs and hybrids.

But its not just pedestrians and other road users that are at risk, the absence of an engine note deprives the driver of one of his, or her, main sensory inputs. A fact brought home to me last year when driving Mercedes-Benz electric SLS — it was an eerie experience with speed only accompanied by a combination of faintly whirring electric motors, tire rumble and wind noise.

AMG, who is engineering the car for Mercedes, told me they are researching a suitably synthetic sound for when the car goes on sale.

Later this year the first production car with a Lotus Engineering developed system that will enhance the in-cabin engine note will go on sale.

Lotus has further improved its Halsonic sound creating system further by linking it into a camera based pedestrian detection technology so that the external noise is generated only when a pedestrian, or cyclist, is detected about 40 feet from the approaching car. The software calculates the approaching speed and if it determines the pedestrian will be safe, the warning engine note will not be broadcast.

An external microphone allows the software to measure ambient noise and increase or decrease the volume accordingly.

Lotus and its partner, Harmon Kardon, have created synthetic engine notes that are similar to whatever powertrain youd like, ranging from a twin-cam four right through to a V-12, complete with rising engine revs and gear changes, although I have to admit they do sound a bit like a games arcade at times.

Japan has already mandated that EVs and hybrids should sound like cars and not some sci-fi, Star Wars synthesis. They will even incorporate an artificial tick-over so others are aware the car is active.

OEMs might even want to develop their own sound signature in the way that a Porsche or Harley Davidson is instantly recognizable; they might even create downloadable engine notes. But one thing is certain – future cities populated by EVs and hybrids wont be totally silent, maybe just a bit quieter.