A universal sound for e-scooters is being developed by scientists at the University of Salford working with the Royal National Institute for Blind People (RNIB) to help pedestrians hear the oncoming vehicles. The silent motors of e-scooters can be dangerous for people who expect to be able to hear hazards approaching on roads and pavements, and the researchers have gained funding to explore a range of audible motor sounds to find one which is sufficiently noticeable to help safety, while being pleasant for those around, and avoiding unnecessary urban noise pollution. Dr Antonio J Torija Martinez, the project’s principal investigator, said: “Based on initial research, we found that the addition of a well-designed acoustic signal can significantly increase vehicle awareness and ultimately safety.” Working in conjunction with the e-scooter hire company Dott, the researchers will now explore the impact of different tones on users and the public across Europe, working with international blind associations. Rather than simply playing a uniform tone, the project is exploring the possibility of a scooter making an artificial sound that reflects its speed and thrust, matching the expectations people already have based on experience with petrol engines. “Light electric vehicles pose a significant safety hazard to many people with sight loss,” said Robin Spinks, the strategic lead on innovation projects at RNIB. The researchers deployed a mathematical measurement of the annoyance and pleasantness of various sounds in an effort to find the best option for the scooters: something too annoying would be inappropriate for use in a busy city but something not annoying enough might risk being hard to notice in an emergency situation. Then, the best candidates for the note were put through an experimental trial. Test subjects were placed in a VR environment and told to press a button on a controller as soon as they detected a moving hazard; at the same time, they were given a brief passage of text to read and answer questions on, to simulate the distraction of a busy street. In the end, the winning sound was a “broadband” sound – one containing an even mixture of noise in both low and high frequencies – mixed with a “modulated tone”, a clear single note distorted slightly. The mixture mimics the sound of a car, which has a broadband noise generated by the tyres on the road and a tonal sound generated by the engine itself. The work follows on from a trial carried out by TfL in January 2020 to explore the possibility of playing a similar warning sound for electric buses travelling at low speeds.