Driving an electric vehicle in near silence can be a joy for those who don’t relish the rumble and whine of an internal combustion engine. But this hushed operation can be difficult to hear from more than a few feet away, making it a deadly problem for the vision-impaired who can’t see a vehicle approaching.

Equipping such vehicles with audible alerts is vital, says Claire Stanley, an advocacy and outreach specialist for the American Council of the Blind.

“As blind individuals, we learn to travel across streets and maneuver through cities by reading the sound of traffic around us,” she said. “But the silent nature of electric cars suddenly robs us of such clues.”

Governments around the world have told automakers to turn up the volume for the safety of pedestrians and cyclists. Japan issued guidelines for acoustic vehicle alerting systems in January 2010, with the United States and the European Union announcing regulations soon after. But the requirements differ among countries, both in terms of what the warning sound can be and when it should activate.