New sounds are being synthesised by engineers to make notoriously quiet hybrid and electric vehicles (EVs) noisier, but groups representing blind people have warned vague European Union regulations could mean the green cars will remain virtually silent at speeds of under 20 miles-per-hour.

Campaigners concerned about the safety implications for pedestrians with sight loss say that drivers can currently silence artificial engine-type noises at the push of a button, meaning EVs will continue to present a potential hazard to the visually impaired.

Though many EV manufacturers have created what they call “virtual engine sound systems” for the machines to emit, E&T can reveal that at least one car company, Audi, is yet to do so and refuses to say if it will comply or not with EU regulations obliging such measures to be in place by 2019 at the latest.

Guide Dogs for the Blind and the Royal National Institute of Blind People (RNIB) are among the organisations worried that electric cars are currently far too quiet to be heard, particularly when travelling relatively slowly.

The British Horse Society has also raised concerns that the equine animals, which are used to listening for the hum of the internal combustion engine when being ridden on roads, could also be adversely affected by all-too-quiet EVs as their take-up among motorists increases.

Even some longstanding campaigners against noise pollution share their disquiet. John Stewart, the author of The Noise Climate Post-Brexit, said: “Silent cars would dramatically reduce noise, but what the RNIB is saying has some real validity.

“I would accept there does need to be some noise from vehicles when they are moving, otherwise there is a real problem as far as safety is concerned – not just for blind and partially sighted people but for the general population.

“A lot of us, when we are crossing the road, rely as much on hearing as on sight and other senses.

“Much as I would love to have completely silent cars, I’m not sure in the real world that would actually be possible.”

He said he feared “brand-specific noises” akin to the Nokia ringtone, possibly bearing scant resemblance to the sounds produced by a traditional car, would be created by some manufacturers as a means of effectively advertising their product for free.

Stewart said: “The key is what kind of noise is added. It may not be the loudness of the noise that is all important. For example, if it was a low-frequency noise, that may be disturbing, or if it was a high-intensity noise, that may be annoying. The onus is on the manufacturers to market test, with focus groups and elsewhere, the kind of noises that would be most acceptable to people.”

He described current EU regulations on noise from electric cars as too non-specific and toothless to be of much use.

Hugh Huddy, from the RNIB, said: “The very low sound levels on electric and hybrid cars make them a potential danger to blind and partially sighted pedestrians like me, because we need the sound of a vehicle to know it is there.

“I recently experienced first-hand how the dangers of a quiet car can play out on a zebra crossing. Having listened for traffic and heard nothing coming, I proceeded to cross, but my cane became jammed under the rear wheel of a car silently moving off the zebra, which broke the end of my white cane.

“However, the outcome could have been a lot worse and as the number of electric and hybrid vehicles on the road increases, we urge manufacturers to equip them with effective audible warning sounds, so blind and partially sighted pedestrians can hear them and avoid them when crossing roads and shared spaces.”

Though the EU has stated there needs to be “harmonisation” of what it calls “acoustic vehicle alerting systems”, Guide Dogs for the Blind complains of a “lack of consistency” in the artificial noises being emitted by EVs.

Nissan, which manufactures the electric Leaf, confirmed it has installed a “pedestrian alert” across this range. This is described as “a complex sound that sweeps from 2.5kHz at the high end to a low of 600Hz when the vehicle is travelling under 20 mph, alerting nearby pedestrians to the vehicle”.

A spokesman for Renault said some of its EVs had technology that emits an audible warning to inform pedestrians and cyclists of the vehicle’s approach.

However, although its default setting when starting the car is “on”, drivers can simply press a button to silence it.

The Renault Kangoo ZE includes a warning sound as standard but allows drivers to select from three different noises – something that could create confusion among pedestrians with impaired vision when trying to cross roads.

A spokesman for Renault said: “On the Twizy, the driver can engage a feature on one of the steering columns that provides a beeping noise in order to increase awareness of its approach.”

Audi admitted there is no synthesised noise in its current e-tron range of EVs and said it was “unable to comment” on whether any future technologies would be deployed.

A spokesman for Hyundai stated: “The IONIQ EV has a ‘virtual engine sound system’ which generates an engine sound so pedestrians can hear the vehicle whilst it is operating.”

Again, however, this function can simply be turned off by the person at the wheel.

Oxbotica, whose autonomous electric “pods” are being used as part of a pilot project in London, said its vehicles contained noise generators to ensure people are aware of their presence.

Neither TESLA nor BMW replied to E&T’s request for comment.