What’s wrong with being quiet?

by aturne on March 8, 2013

Ford C-Max Plug in Hybrid

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.

Image courtesy of photopin.com

Normal Car * 4 Cylinder Engine                                                        Synthesized Sound

*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.

My take

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?

Michael March 9, 2013 at 1:38 am

Easier still, connect the the car stereo to the outside.

Nirlesh March 9, 2013 at 4:30 am

Concept is good but still far more needs to be done.

Jennifer March 9, 2013 at 3:02 pm

The lack of noise is also a big problem for cyclists and in particular children learning to safely ride on the road.

Angela March 12, 2013 at 12:25 pm

Ha – your post reminded me of hours spent in my friends’ (very loud) street facing flat trying to imagine with them what the same traffic would sound like if it was made up of electric cars. The noise attentiveness is probably also a cultural thing. In the UK and the US, for example, people tend not to look out for bicycles so much, so many pedestrians end up having bicycle collisions. In Germany, the Netherlands and Scandinavia, people tend to look out more for bicycles, as they are so ubiquitous. The question is whether you’d want to sacrifice a generation 😉
Your transport transition theme also reminded me of discussions of ‘horse to car’ issues. E.g. here is an example: http://www.uctc.net/access/30/Access%2030%20-%2002%20-%20Horse%20Power.pdf It would be pretty funny to outfit an electric car with an overpowering smell of some kind (or animal noises?) at low speeds as an alternative sensual cue…

David March 15, 2013 at 9:06 am

An extraordinarily interesting topic! I suppose I’ll play the devil’s advocate here and take the position that maybe we should simply encourage increased driver and pedestrian awareness? It may sound curmudgeonly, but I don’t necessarily think that people should walk (or run, or cycle) around with noise blasting in their ears, unaware of the world around them.

The problem becomes more complicated with regards to the visually and hearing impaired, certainly, and I agree that steps need to be taken to ensure the safety of these populations. However, I don’t think it’s too much to ask to merely require increased driver attentiveness?

Adam.R March 28, 2013 at 8:15 am

This was a very interesting blog. I liked how you gave an example of the car sounds with the recording and I also liked how you gave a personal experience of how you realized how quiet these cars are. Though hybrid cars and electric vehicles have a long list of advantages and benefits to the environment, their low noise level is a problem for safety. The way that the engineers solve this noise problem is, in my opinion, the best solution for this problem. Hybrid vehicles and electric vehicles are an amazing achievement in engineering, but even they have problems too. Also, new hybrid technologies are being incorporated into new super cars and hyper cars that are coming out soon to help reduce fuel consumption and greenhouse gases and as we all know, super cars and hyper cars are very loud and a pedestrian will hear one from kilometres away. I was wondering if these hybrid and electric technologies could be incorporated into these hybrid and electric vehicles to make them sound louder?

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