As electric vehicles become increasingly common, concerns about their safety, particularly for vulnerable road users such as pedestrians and cyclists, have grown. Unlike traditional internal combustion engine vehicles, electric vehicles are much quieter, which can make them harder to detect, especially at low speeds. To address this issue, many countries have implemented regulations requiring electric and hybrid vehicles to emit warning sounds when traveling at low speeds.
Researchers at Chalmers University of Technology in Sweden have conducted a study to investigate how well people can locate the warning signals emitted by these vehicles. The study, published in The Journal of the Acoustical Society of America, tested 52 participants in an acoustics laboratory using soundproofed, anechoic chambers. The participants were surrounded by 24 loudspeakers placed in a ring at chest height, simulating the sounds of electric and hybrid vehicles moving at low speeds.
The researchers found that the warning signals used by many electric vehicles are significantly harder for humans to locate than the sound of a traditional internal combustion engine. One particular signal type, consisting of two tones, proved to be especially challenging, with none of the test subjects able to locate all instances of this signal within a ten-second time limit when multiple vehicles were simulated.
The study’s findings have important implications for traffic safety. While current regulations focus on ensuring that electric vehicles are detectable, they do not address the issue of localization – that is, being able to determine the direction from which the sound is coming. This can be particularly problematic in environments such as car parks, where multiple vehicles may be moving simultaneously.
“The requirements placed on car manufacturers relate to detection, not about locating sound direction or the number of vehicles involved,” said Leon Müller, a doctoral student at Chalmers University of Technology. “But if you imagine a supermarket car park, it’s not inconceivable that several similar car models with the same AVAS signal will be moving at the same time and in different directions.”
The researchers are calling for further studies to investigate how people react in real-world traffic situations involving electric vehicles. They also suggest that new signal types may be needed to improve localization while maintaining detectability and minimizing negative impacts on people in the surrounding environment.
The study’s findings highlight the need for a balanced approach to addressing the safety concerns associated with electric vehicles. While they offer many benefits, including reduced noise pollution, their quiet operation can also pose risks to vulnerable road users. By developing warning signals that are both detectable and locatable, manufacturers can help to ensure that the benefits of electric vehicles are not compromised by safety concerns.
