Right to Quiet Society Noiseletter
Fall 2013, page 4

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Pedestrian alert sound system on hybrid and electric vehicles

With the emergence of quiet hybrid and electric vehicles, concerns about pedestrian safety arose. Some members of the Right to Quiet Society submitted comments to the Environmental Assessment Panel, National Highway Traffic Safety Administration (NHTSA), Department of Transportation (DOT) in the USA on the issue of equipping quiet electric vehicles with an alert sound for pedestrian safety. Following below are two of these comments:

Dear NHTSA and DOT panel members,

I suggest that you take the “No Action” first opinion for now, pending the development of a more intelligent, comprehen-sive, active, and driver/politically acceptable alert system. In this day and age it should be no problem to equip cars to detect the presence of people and other warm-blooded creatures in the vehicle’s vicinity. Such devices have long been in use for security systems (“passive infrared”, low-energy microwave and other back-scatter systems).

Moreover, the present options assume good hearing on the part of the pedestrian. Any such system should be expanded to alert the hearing impaired to the presence of any motor vehicle - by means of perhaps a low-energy transmitter retrofit and a pedestrian pocket vibrator. (Parents/Guardians might want to equip kids and other dependants with such devices as well.) Both the audible device and radio frequency transmitter need only broadcast approximately 50-foot-range signals when people (and animals - deer, for instance) are detected - and why not alert the driver as well?

An even broader system would use unique, longer range signals for public and school buses, such that children (and especially the hearing impaired) would not have to be at risk, waiting street-side in the dark, cold and rain.


Craig Daniels

Dear members of the Environmental Assessment Panel,
National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT),

The issue of a "Pedestrian Alert Sound System on Hybrid and Electric Vehicles" should really be given much more thought and exhaustive consultation with interested parties and the general public, as this addition of sounds to a growing number of vehicles will undoubtedly have an increasing detrimental impact on the soundscape, the indispensable acoustic component of the environment, very important to the health of humans and other creatures. Ideally, this matter should be resolved by using non-audible warning signals, which, for the vision-impaired traffic participants, could be a small gadget vibrating in the person's pocket, just like a call-alert on a cell-phone with the ringer shut off. In fact, modern technology makes it quite possible to implement much more of noise-free warning signals, all of which would make the added sound on "silent" vehicles practically redundant. If, in addition to that, all other types of noise would be reduced to a minimum, even the so called silent vehicles could be heard, since they are not truly silent.

If then some low-level sound (i.e. no more than 35 to maximally 40 dBA at 10 feet or 3 metres) would still be deemed necessary, that type of sound certainly ought to be regulated and standardised to avoid unwanted competition. Otherwise, manufacturers and drivers would quickly come up with a multitude of sounds, creating a chaotic cacophony. You may think 40 dBA is not loud, but consider that there will often be several vehicles "sounding off" simultaneously. With each 40 dBA added to the first one, the sound-pressure level doubles, all of which would be a terrible burden on an already often strained soundscape. The fact that ever more people get hard of hearing should not be taken as an excuse for increasing the sound-level. Quite at the contrary, all this growing hearing impairment is primarily due to ever more exposure to noise, for which all noise should be reduced or prevented in the first place.

In your NHTSA-2011-0100-0001 Document I didn't see any decibel levels mentioned, only references to other types of sound. If manufacturers were to build in on-off switches for the "added alert sound" to be turned on or off by the drivers, it would be very interesting to do a comprehensive opinion poll to get an idea of just how many drivers would actually bother with that, respectively how many drivers might misuse this discretion for the pursuit of a personal whim. One of the psychological effects of the added sound could be that people come to rely on it to the point that they won't pay due attention anymore to visual cues. One such example are the warning beeps of descending wheelchair ramps on buses. I am paraplegic and observe almost each time I use a bus how other passengers or pedestrians totally ignore this warning signal, I suppose because there is already so much other noise, particularly warning sounds and "digi-noise" around. And many times I see traffic participants, especially cyclists and pedestrians, not looking first before stepping off the curb. I suggest to keep the noise low and rigorously educate and train people!!

Hans Schmid
Right to Quiet Society

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