What do the blind, small children, cyclists, runners and other pedestrians have in common? A reliance on sound. Which, when it comes to electric vehicles, can be a major problem. I'm talking about the same electric silence that is so environmentally and driver friendly. The gentle hum of an electric engine says 'I'm synergy' when pedestrians expect more of an 'I'm coming, get out of the way'.
Electric cars produce enough sound at higher speeds, between tires on the road and wind resistance, to overcome that electric-induced silence. The main concern for pedestrians is at speeds between 0 to 18 mph. At the moment the European Union is processing legislation that will require electric vehicles to have pedestrian warning sounds at low speeds by the year 2019. The US and Tokyo have passed laws regulating electric vehicle warning sound equipment, but with no mandatory measures. These sounds range from obviously artificial to more subtle notes. More or less you can expect electric vehicles to emit varieties of Star Wars or to have a more familiar tires-on-gravel sound.
The National Federation of the blind have been among the most active in drawing attention to the threat that electric vehicles pose to pedestrians (and, inherently, the blind). The federation funded a research project in 2008 that showed late pedestrian detection of electric vehicles, finding that in most cases reaction time left as little as one or two seconds before impact. The study, performed by the University of California, determined that the greatest risk came when the electric vehicles weren't moving in a straight line - i.e. parking lots or during turns. Participants of the study could typically detect an internal combustion engine (traveling 5 miles per hour) at 36 feet. Electric vehicle detection at the same speed, however, averaged at a mere 11 feet.
Pair that with a study in 2009, performed by U.S. Highway Traffic Safety Administration, and the chilling end result is clear - more pedestrian accidents involving electric vehicles in slow speed maneuvers. Accidents were common during daytime and in clear weather. And compared to internal combustion vehicles, electric vehicles have double the potential for accidents involving pedestrians. With the instillation of artificial sound on electric vehicles that potential drops significantly.
And thus comes into play a Danish company named Delta. Because while a warning sound for electric vehicles has to be heard, electric transportation doesn't have to be distracting. A delicate balance between audibility and sound pollution is at play. Delta's lab, Senselab, has a range of electric vehicle sounds it rates in units of 'suitability' and the research will make for an alert - but happy - electric vehicle to pedestrian relationship.