Should electronic vehicles make noise?

Members of the European Parliament have voted to make ‘Acoustic Vehicle Alerting Systems’ mandatory for all electric and hybrid vehicles in 5 years time. [1] But is this a good idea? I have a personal reason to question whether the claims of improved road safety are right.

The legislation has arisen because there are fears that hybrid and electronic vehicles are too quiet at low speeds, making it hard for pedestrians to hear them coming. Companies are experimenting with playing noises from loudspeakers hidden under the hood to alert pedestrians. But what sound should they use? Why, something familiar that immediately makes pedestrians think “vehicle.” Here is the space-age hum that Nissan has opted for:

In one scientific experiment, however, people preferred the noise of an internal combustion engine over hisses, hums, and whistles. [2] There is a legacy of old sounds surviving from obsolescent technologies. As a correspondent to New Scientist wrote, “Imagine if this concept of familiar sounds had been developed earlier. Would cars all make the sound of horses’ hooves instead of the new fangled and confusing drone of an internal combustion engine?” [3]

So why am I against the use of alerting sounds on electric cars? It might surprise you to hear it has nothing to do with my work as an acoustic engineer and the lost opportunity to reduce noise levels in cities. I would rather electronic cars were quiet because I think that my commute would be safer.

I am currently recovering from a broken shoulder caused by someone stepping off a pavement in front of me and a fellow commuter who were using silent vehicles (bikes). One of the hazards of riding a bicycle in a crowded city is that pedestrians sometimes rely too much on their hearing and don’t look out for cycles. I would prefer electronic cars to be silent because it might encourage pedestrians to be more observant.

I’m not an expert in road safety, but I fear that alert sounds are an engineering solution that is overlooking behavioural changes by drivers and pedestrians. A study in Germany showed that drivers of electronic vehicles adjust their evaluation of noise-related hazards, and concluded that the ‘dangers associated with low noise emissions might be less significant than previously expected.’ [4]

The evidence on whether electronic cars cause more accidents is mixed. A study in the US showed hybrid cars were involved in more low speed crashes with pedestrians and cyclists than would be expected from the number of hybrid vehicles on the road. But in Japan and the Netherlands no increased risk was seen. [5]

What do you think? Should electronic cars make artificial noise?



[2] P. Nyeste and M. S. Wogalter, “On Adding Sound to Quiet Vehicles,”
in Proceedings of the Human Factors and Ergonomics Society 52nd Annual
Meeting—2008 (Human Factors and Ergonomics Society, 2008), 1747–50.




12 responses to “Should electronic vehicles make noise?

  1. I’m all for keeping electric cars quiet. More space to hear the wind, birds and especially silence. The less artificial noises created the better. People should learn to be more observant whether behind the wheel or in the cross walk. Also has there been studies done to see if over time electric cars become more noisy? The BART transit system in the bay area was touted as quietest train system when it was built. Now you can hear it for miles.

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  3. Damian Kearns

    Hi Trevor. I’m sorry to read about your shoulder. I hope you heal quickly. I think cars ought to make some noise to alert pedestrians to oncoming traffic. It’s true pedestrians should be more diligent and so should drivers. But, it’s human nature to let diligence lapse at times and it’s often those moments in which accidents occur. If a vehicle can be programmed to sound an alert to people in its path, I think it should be done. There are also environments where sound is the only clue one has that traffic is approaching. I’m thinking of winding country roads and other sharp turns.

  4. As a cyclist and noise policy specialist I find your argument for keeping electric cars quiet convincing. Increasingly urban pedestrians (and, admittedly, some cyclists) roam the streets cocooned in headphones, like drivers cocooned in cars, oblivious to what’s going on around them. A common pedestrian reaction to an oncoming cyclist glimpsed askance is to put the head down and step out regardless – most motorists (there are always exceptions) – do look when they pull out. As a cyclist, I have been caught out by smart cars pulling out and the odd Prius as it reverses silently when have not been looking properly. We could develop a world filled with generic warning sounds ranging from reversing alarms to bike bells and electronic car noises – but isn’t it better that we all learn to become conscious of what’s around us and maybe take things a bit more slowly and carefully? Agree on country roads sound important – however at speed road/tyre noise is the predominant sound – and given the current state of rural roads I think we will hear them coming.

  5. I’m from the keep them quiet, reduce noise in our cities school, but in answer to Damian’s comment, and in a response to the EU vote, I would encourage car manufacturers to design more intelligent systems, that make noise only when needed. It is not beyond our engineering to compensate for vehicle speed, proximity of other objects, geographic location etc and adapting the sound to this.

  6. An interesting view, to which I can see both sides of the argument. I understand that we need people to be more aware as this would solve many problems, but at the same time I don’t think an increased likelihood of being hit by a car is going to make much difference judging by the way many pedestrians seemed to cross the roads nowadays!
    It is a dilemma though and it’s one which is not made easier by the headphone culture where people seem to completely zone out from the world as they go about their daily business (I say this, yet I am sure I am just as much to blame as the next guy!). This reminded me of Apple’s latest patent I saw this week for a “see-through” iPhone… I can’t quite work out whether it’s good for safety or will simply encourage more people to text and walk!?!

  7. Ulf Sandberg has thoroughly reviewed this issue, Dec 2012 paper at link below. He argues against increasing vehicle noise and suggests reducing ambient noise overall, and hence lessen masking, would be a better strategy providing a greater overall benefit for society. He also suggests that there is scant evidence to support either that it is a problem in the first place or that increasing electric vehicle noise is going to be of significant benefit.
    Analagous to this issue is reversing alarms, which at the moment I am hearing all day from a construction site next door, the site being surround by several large apartment blocks (100s of units). We have all been disturbed by this for weeks with no apparent benefit to safety, there generally being no people on the site other than the drivers of the earth moving vehicles.
    I have also undertaken a number of quarry noise impact assessments where the only noise causing disturbance to closest residents, and for which noise mitigation is not permitted because it is to do with safety, are the reversing alarms.

  8. Wouldn’t a focused sound system, both fore and aft, controlled by a proximity detection system be the best answer? Just like light pollution, sound pollution needs to be controlled and thousands of noise emitters rolling around cities and towns, putting out noise in directions that it’s not needed, seems terrible. A “horn button” for the driver could turn up the warning noise power and perhaps broaden the sound’s cone for emergencies but the general sound level and pattern would be tightly controlled to only the direction of travel and only to the distance of a vehicle’s emergency stopping distance.

  9. In lieu of manufacturing engine noise on electric cars, they should just be equipped with sleigh bells.

    Making electric cars noisy is asinine. Some pedestrians were hit by cars that by happenstance were electric, so rather than accept culpability, they made a presumptive correlation that it’s because the cars were too quiet.

    Prior to legislation some real-life testing needs to be done. The majority of people do not hear the engine noise of most vehicles over the din of city life. The primary safety cues are vehicle movement, vehicle occupancy, and road noise.

    It’s really no surprise that jaywalkers are getting hit. Yet there hasn’t been a surge of blind pedestrians hit by electric cars…because despite white cane laws and being able to hear traffic, blind people cross streets at intersections. (I realize it’s also because they use mental maps.)

    PS: A cyclist myself, I sympathize for your injury. I don’t use a bike bell, but am a very vocal rider. As I’m sure you do, I make every effort to acquiesce to pedestrians despite my right-of-way…both for courtesy and safety. Though no matter my best efforts people still jump out in front of me, and of course, once one leads the crowd follows. Maybe I should attach sleigh bells to my bike too.

    As to my safety as a pedestrian, since it seems like I’m always being bumped into, I sometimes contemplate the following solution for crowded places. Enjoy.

  10. I am visually impaired. No amount of awareness except audio feedback will allow the blind and visually impaired to hear approaching vehicles. I believe there should be some uniform sound that duplicates engine noise so that the blind can identify approaching cars. An electronic whirring sound could be confused with a stationary object like an air conditioning condenser. The alerting sound should sound like what we identify as a car, truck, motorcycle, etc. Given the fact that the blind aren’t driving or whizzing through traffic on bikes, we tend to be the most vulnerable in traffic to begin with, and have no choice but to be pedestrians. It’s not just noise to us….it’s a matter of life and death for the blind.

  11. Have been thinking about this a lot.

    The dutch solution to the bicycle safety issue is to have your mudguards rattle constantly as you roll down the road.

    There’s doubtless something mechanical that can be fitted to a motor which will cause it to generate a sound. It is also possible to design tires for high ground noise rather than low ground noise.

  12. The solution of pedestrians being more observant isn’t viable for all parties. As a teacher of the visually impaired, someone who is blind/visually impaired relies on these sounds to travel independently. That is the major concern. How can you tell someone who is blind to “be more alert” when they rely on their auditory senses, and these cars lack the sound?

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