Hybrids, PHEV and EVs Too Quiet?

MAY 15 2012 BY MARC LEE 6

This article from Slate points to some numbers from a NHTSA report that reportedly show that Hybrids and EVs are more dangerous to pedestrians:


That’s because NHTSA studies in 2009 (pdf) and 2011 (pdf) confirmed what many long suspected: Hybrids and electric cars are too quiet for the blind or even the fully sighted to hear them coming. Though the NHTSA found little statistically significant difference in collisions over 35 mph—when wind and tire noise negate the difference in engine noise—at lower speeds, hybrids and electric vehicles are 37 percent more likely to hit walkers and 66 percent more likely to collide with cyclists than traditional gas-powered cars.


NHTSA is tasked with starting the process to develop rules for “minimum” car noise this summer.

If the studies above are valid I guess it is necessary, but alas consider the joy of walking through cities like NYC or SF in the not so distant EV dominated future and hearing only the gentle hum of tire on asphalt.  I wonder if in fact, in that quieter atmosphere if EVs don’t already make enough to be heard, its only the din of all the existing gas engines the covers up their softer foot falls.

The BMW i8 Spyder features sound generation, which is cool at first, but I could see it being annoying after a while, and certainly the combined cacophony of scores of EVs with generated sound would be downright irritating.

NHTSA suggests that volume levels below what most gassers produce would be sufficient to warn pedestrians.

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6 Comments on "Hybrids, PHEV and EVs Too Quiet?"

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I’ve had a good number of discussions with the electric vehicle managers over at BMW about this and I’ve practically begged them to really consider if this is necessary before they willingly accept that EV’s need artificial noise.

The MINI-E and ActiveE programs have been ongoing for a combined three years now and the cars have logged over 5 million total miles and to my knowledge, and to the knowledge of the electric vehicle program managers, not once has there been a vehicle to pedestrian accident.

The EV industry is so new, there just isn’t any credible data to prove quiet electric vehicle pose a greater risk to pedestrians. Can’t we at least have a real study done before we rush to legislate?

Anyway, it looks like BMW listened to me because they just announced they don’t plan to use artificial noise on the i3 when it comes out next year because they don’t believe it’s necessary.
Of course if the government forces them to add it, there is nothing they can do.

I think it would be easy for some sound engineer to mock up the street noise that a pedestrian would hear in some distopian future where EVs comprise 25 percent of the traffic. It would be very informative to those making policy. It seems that technology available to hearing impaired today or in the near future would be a more appropriate solution to this – an iphone app that identifies oncoming traffic or dangerous situations.

Ocourse it would be funny to see something like ‘DAS AUTO’ coming out of a german car. And ‘Zoom Zoom’ from a nissan.

My 2011 Leaf has a noise generation, but I can turn it off. Unfortunately it also turns off the back-up chime, which I like. The 2012 Leaf does not include the feature to turn it off. This is probably why the car comes with such a wimpy horn. You can use it to warn a pedestrian without scaring him to death. I replaced my horns with real car horns as a safety feature in my city’s crazy traffic. I also added a “Bermuda Bell” to warn pedestrians and bicyclists and it works very well.