I like the quiet. Right now it is especially quiet because all of the college kids have gone off someplace warm for drinking and merriment during spring break. This excessive noise or noise pollution can cause aggression, hypertension, high stress levels, tinnitus, hearing loss and sleep disturbances.
One small way to reduce the noise is with Hybrid Electric Vehicles (HEV) and Electric Vehicles (EVs). On average these machines are significantly quieter than traditional cars because they have an electric engine. Plus there’s an entire laundry list of other potential benefits to both hybrids and EVs.
But what about the negatives?
The lack of sound from HEV and EV may present a problem for pedestrians. When driving at low speeds both types of vehicles do not produce enough sound to alert pedestrians. A lack of sound can affect people who are walking, running and cycling. I’m picturing a runner right now with headphones unable to hear the approaching vehicle. But another area of greater concern is for the blind or visually impaired.
What’s a pedestrian to do?
The potential difficulties related to quiet HEV and EVs was discussed as early as 2010 in the Pedestrian Safety Enhancement Act of 2010. Very recently the National Highway Traffic Safety Administration (NHTSA) -link published their planned “quiet car rule”. It requires HEV and EVs to sound like…well…cars. It is expected that this new regulation will prevent injuries, accidents and loss of life.
How do we do it?
The solution is actually quite simple. Engineers incorporate synthesized car sounds to hybrid and electric vehicles. The quiet car rule enables automakers to create a custom sounds for each make and model. The vehicle’s car sound will reflect the car’s actions to indicate idling, accelerating, decelerating and cruising. The synthetic sounds will kick in when the vehicle operates below 18 mph. A vehicle running at above 18 mph has significant sounds from its tires and wind resistance to inform pedestrians of their presence.
*both are recordings at 10 km per hour at a constant speed
What does the research say?
The decision to require synthesized car sounds came from a NHTSA study. In it they tested the ability to detect a electric or regular vehicle. Three possible scenarios were tested including: backing up at 5mph, slowing down 20-10mph, and a vehicle approaching at a slow speed. Participants were asked to detect the vehicle on an audio recording. The researchers looked at whether or not the participants could detect the sound and when they detected it. All participants were able to detect the sound. However, when listening to EVs and HEVs the participants detected the sounds significantly later in all scenarios except the backing up. The inability to detect this form of vehicle demonstrated the potential health hazard and the need for synthetic cues.
I had my first ride in a plug in hybrid this week, which informed this week’s blog post. From my experience I can attest that plug in hybrids are quite quiet. But I don’t think the problem is limited to the blind. In fact, in NHTSA’s study participants were asked to listen for sound. What happens when you aren’t paying attention? Or listening for sounds? Any pedestrian could be at risk. It’s an interesting tension to have, trying to reduce sound or pedestrian safety. How do we decide which health problem has greater precedence?