Don Norman:

It was a pleasant June day in Munich, Germany. I was picked up at my hotel and driven to the country, farmland on either side of the narrow, two-lane road. Occasional walkers strode by, and every so often a bicyclist passed. We parked the car on the shoulder and joined a group of people looking up and down the road. “Okay, get ready,” I was told. “Close your eyes and listen.” I did so and about a minute later I heard a high-pitched whine, accompanied by a low humming sound: an automobile was approaching. As it came closer, I could hear tire noise. After the car had passed, I was asked my judgment of the sound. We repeated the exercise numerous times, and each time the sound was different. What was going on? We were evaluating sound designs for BMW’s new electric vehicles.

Electric cars are extremely quiet. The only sounds they make come from the tires, the air, and occasionally from the high-pitched whine of the electronics. Car lovers really like the silence. Pedestrians have mixed feelings, but blind people are greatly concerned. After all, they cross streets in traffic by relying upon the sounds of vehicles. That’s how they know when it is safe to cross. And what is true for the blind might also be true for anyone stepping onto the street while distracted. If the vehicles don’t make any sounds, they can kill. The United States National Highway Traffic Safety Administration determined that pedestrians are considerably more likely to be hit by hybrid or electric vehicles than by those with an internal-combustion engine. The greatest danger is when the hybrid or electric vehicles are moving slowly: they are almost completely silent.