A recent study by the Belgian road safety institute Vias shows that electric vehicles are more frequently involved in accidents with vulnerable road users. They are involved in 42% of injury-causing accidents involving electric cars, compared with 27% for all car types.

Vias analyzed whether the lower noise levels of electric and hybrid vehicles could affect the safety of vulnerable road users. Particular attention was paid to people with visual impairments, who are most affected by the lack of noise.

One possible explanation – although not necessarily the cause – is the lack of noise EVs make. Especially at low speeds, electric models make less noise, are noticed later, and are harder to locate than vehicles with internal combustion engines. Vias advocates raising the minimum noise standard and harmonizing standards across brands.

Legal frame

To address the issue of quiet EVs, the European Union has introduced the ‘Acoustic Vehicle Alerting System’ (AVAS) for all electric cars. This is an artificial sound that all electric vehicles must produce. In other words, electric cars are legally required to produce a specific sound at low speeds.

However, its effectiveness is sometimes called into question. Recent research by Vias has shown that this sound is often not loud enough and, moreover, varies across brands. The institute believes this needs to change, especially as the number of electric vehicles continues to grow. Over the past five years, the share of electric or hybrid cars in our country has risen from 3% to 20%.

Noise measurements

During the study, various noise measurements were conducted on a closed circuit using five vehicles (three with internal combustion engines and two electric) performing various maneuvers (driving at a constant speed, decelerating, accelerating, and reversing).

Op top of that, Vias had 70 participants, half of whom were blind or visually impaired, who listened to recordings of ICE, electric, and hybrid cars against several levels of background noise. The percentage of cars participants failed to detect was:

The results show that at a speed of 10 km/h, all internal combustion engines produce a comparable noise level (approximately 55 dB), whereas electric cars equipped with an active AVAS system differ from one another. 

At 10 km/h, hybrid and electric cars are more often undetected than cars with internal combustion engines. At 20 km/h, 18% of hybrid vehicles go undetected, compared to 11% for internal combustion engine cars and 7% for electric cars.

In general, blind or visually impaired people had slightly more difficulty than the control group in detecting cars when there was little background noise. At low speeds, cars are not always noticed in time by vulnerable road users. This is certainly true for blind and visually impaired people.

Sound design matters

In the study, Vias demonstrated that sound design matters, and therefore recommends improving the system in several respects: standardizing the sound used, raising the minimum sound threshold (within reasonable limits to prevent noise nuisance), and focusing on frequencies that are more effective at enhancing the detectability of electric vehicles.

One thought regarding the study, though: EVs are never truly completely silent when driving. After all, there is always the sound of the tires – tire/road interaction – as well as bearings, drivetrain noise, and ultimately aerodynamic noise.

Other vehicle noises

Research on vehicle noise has even found that tire-road noise can be the largest component down to around 20 km/h, depending strongly on the tire, pavement, and vehicle.

The Dutch SWOV (National Scientific Institute for Road Safety Research) made the same point years ago: on Dutch 30 km/h streets with rough paving or klinkers, tire-road noise can dominate, making an EV perfectly audible.

To conclude: The Vias study has indicated that a slowly moving electrically driven vehicle can be harder to hear, particularly for people relying heavily on auditory information, which is a solid argument for improving and perhaps harmonizing AVAS sounds.