Lotus Engineering - yes, as in Exige - has developed a ‘Safe & Sound’ external sound system which enhances pedestrian safety for quiet vehicles.
It works by literally simulating the sound of a conventional petrol engine through a waterproof speaker mounted at the front of the car.
At low speeds when a hybrid such as the Prius would be running completely silently on its electric motor, throttle and speed dependent synthesised sound projects a realistic engine sound in front of the vehicle.
When the hybrid’s petrol engine starts operating, the control system automatically stops the external synthesis.
The system apparently fills a very real safety void, which up until this point has been the focus of many humorous hyperboles - as seen in this Clarkson review.
Whilst for the average pedestrian the idea seems almost comical, it has been mainly developed for the blind and partially blind who rely heavily on the sound of vehicles when approaching a cross walk.
“Guide Dogs believe further research and development is needed to address the issues of identifying 'quiet vehicles' for blind and partially sighted people. The charity recognises the environmental benefits of these vehicles however more consideration needs to be given to the safety implications to visually impaired pedestrians.”
The engine sounds were recorded using a 'suitable' donor car which was analysed to establish the characteristic frequencies at different engine speeds.
Let’s hope Lotus has at least had a sense of humour when choosing the donor car, and dubbed the track from a Supercharged Exige - expect to hear more high performance Prius' on the road!