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Silent but deadly? Electric cars may be too quiet for pedestrian safety

The views expressed are those of the author and are not necessarily those of Scientific American.


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Fisker,hybrid,engineEnjoy (or fear) the silence while it lasts. Battery-driven vehicles are touted for their potential to cut down on harmful emissions spewed for decades by gasoline-powered cars, but electric and hybrid vehicles may be too quiet to be heard by pedestrians, posing a particular danger to people without sight.

Although the relatively low number of electric and hybrid vehicles on the road as well as the lack of data to link pedestrian injuries to quiet cars make it difficult to validate these concerns, one option being floated is that of "car tones" to make up for the missing engine noise, reports The New York Times. The Times cites Nissan, Toyota, BMW and plug-in hybrid maker Fisker Automotive as companies all considering the addition of sounds that would more prominently announce the presence of their cars on the road. (Stories of Fisker’s plans to use speakers to pump out sounds "like something between a Formula One car and a jet plane" surfaced in March 2008.) "One possibility is choosing your own noise," BMW told the Times.

Congress, already considering the possibility that too-quiet cars could be dangerous to pedestrians, has versions of The Pedestrian Safety Enhancement Act of 2009 in the Senate and House that would direct the Transportation Secretary to study and establish a motor vehicle safety standard that provides for a means of alerting blind and other pedestrians of motor vehicle operation.

The most persuasive argument in favor of noisier electric and hybrid vehicles came last year via a study led by University of California, Riverside, perceptual psychologist Lawrence Rosenblum, who asked blindfolded subjects to listen to recordings of cars approaching at five miles per hour. As reported in the August 2008 issue of Scientific American, subjects could hear the hum of a Honda Accord’s internal-combustion engine 36 feet away. But they failed to identify a Prius, running in electric mode, until it came within 11 feet—affording them less than two seconds to react before the vehicle reached their position.

The noise added to hybrids wouldn’t have to be particularly loud, Rosenblum said, given the human brain’s extreme sensitivity to approaching sounds relative to those that are fixed or moving away. Because the former are more likely to pose a threat, approaching sounds most readily stimulate regions of the brain associated with motor action. Whether it’s a good idea to give drivers a selection of sounds to choose from is an open question. Shouldn’t a car sound like…a car?

Image of Fisker Karmen plug-in hybrid © Fisker Automotive, Inc.





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  1. 1. DiscomBob 3:03 pm 10/14/2009

    This is a transitional issue because people are used to noisy vehicles. Once they become more common and people adapt to the different noise level they will be more sensitive to the noise they do make. I think a lowering of the overall noise level near any road will be highly desireable and it would be a mistake to artificially inject more noise.

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  2. 2. justSlumming 3:13 pm 10/14/2009

    Perhaps we should teach drivers to respect pedestrians right to cross the road instead of increasing the noise pollution.

    Link to this
  3. 3. dennis 3:31 pm 10/14/2009

    They should play "Turkey in the Straw" or "Pop goes the Weasel".

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  4. 4. TTLG 3:35 pm 10/14/2009

    Stupid idea. Are we going to do the same for bicycles? They are quieter than any car. Are we going to make bicyclists ad noise makers to their bikes? How noisy does a vehicle have to be to be "safe"? Where I live tire noise is plenty to be able to hear even a bicycle coming. But that is hardly enough for downtown NYC during rush hour. I wonder what background noise level the UC Riverside study used. I also don’t see why a 2 second warning is insufficient. How long does it take to step out of the way of a car? Besides justSlumming has it right, the driver is responsible to pay attention to pedestrians, not just drive along obliviously.

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  5. 5. bliswell 3:56 pm 10/14/2009

    I recently bought my house knowing that it as alongside a very busy street accross from a park. But I did this knowing/thinking that with time the typicaly automobile will be a quiter EV or hybrid, so the downside being near a loud road will be reduced. With the downside of location reduced, my house would be more valuable.

    Now my investment plan is undermined because Congress wants to legislate oblivious driving and pedestrians who don’t look both ways.

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  6. 6. tharriss 4:04 pm 10/14/2009

    Gee, if one stupid or unlucky person might be at risk, we have to add expense to millions of others, both in terms of dollars and in noise pollution.

    I believe in reasonable safety, but if a person can’t look both ways before crossing, that is their problem.

    I heard that you can get an instant headache from eating ice cream, perhaps we should outlaw icecream or force producers to add heat elements that warm it up before you can eat it.

    Sheesh!

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  7. 7. jonderry 4:18 pm 10/14/2009

    NO NO NO NO NOOOOOO!!!!

    I cannot believe this article. One of the many **benefits** of electric cars is that they are so quiet. What about the added low-level stress and hearing damage caused by the constant din of busy roads?

    Have we forgotten that noise is pollution as well?

    While we’re at it, let’s outlaw mufflers and add a mandate that all cars constantly play loud rap music with booming bass that announces the car’s presence from half a mile away.

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  8. 8. Heyref 4:25 pm 10/14/2009

    I drive a hybrid, and will be happy to turn up the radio a bit more for public safety. I hope you all enjoy the Grateful Dead, Cream, Hendrix, and all.

    Seriously, we need to make things quieter, not noisier. As others have pointed out, we are in a transitional period where people are getting adjusted to the new normal. Relax, be courteous and attentive, and we will all get through this without any new laws being needed.

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  9. 9. spiff 4:32 pm 10/14/2009

    Why not make the sound on-demand instead of constant? Blind people could be given a remote to activate a special noise from the car (like key-fobs for car alarms). Each button press would activate all moving cars within a certain distance to make the sound for 10 seconds.

    This could also be used instead of the annoying chirp sound broadcast at some intersections for walk/don’t walk.

    This would eliminate a lot of noise pollution that is not necessary 99% of the time.

    To go really high-tech, the noise could be virtual, with the blind person carrying a device which would detect nearby car transponders, and make appropriate noises in a headset, directionally correct for the wearer’s orientation.

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  10. 10. adamcatfish 4:36 pm 10/14/2009

    Congress has gone too far already, its time to get rid of these hacks/power hungry criminals.

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  11. 11. adamcatfish 4:37 pm 10/14/2009

    Congress has gone too far already… now this. Its time to get rid of these power hungry criminals/hacks.

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  12. 12. Mr.Tie 4:41 pm 10/14/2009

    I want my car to make a horsey clip clopping!

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  13. 13. analyst1 4:42 pm 10/14/2009

    Better than sending our oil dollars to countries funding terrorists. Quiet is better than loud so you could hear ambulance siren better. REMEMBER PEOPLE. ALL 911 HIJACKERS ARE FROM SAUDI. Osama gets his oil royalty regularly used to kill Americans. I salute people who conserve energy like the Hybrid users and Biofuel users.

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  14. 14. Michael F 5:31 pm 10/14/2009

    I moved to NYC four years ago, and since then I’ve always told friends that live elsewhere that if I had to use one word to describe life here, that word would be "noisy." The thought of adding artificial noise into the mix is so disheartening to me. I understand that this would be beneficial to the visually-impaired, but really, is this the answer? Seems much more like a knee-jerk reaction that will have negative consequences for generations to come.

    As a sidebar, one of the most prominent definitions of "noise" is: "sound that is a disagreeable auditory experience."

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  15. 15. Michael F 5:36 pm 10/14/2009

    Sorry for the back-to-back posts, but I SPIFF’s post just gave me an idea. If something really does "need" to be done, we shouldn’t add more noise. Instead, how about if new cars emit some sort of RF signal (or other non-audible signal) that is able to be detected by a special portable device and translated into some audible warning. That way, the visually-impaired (and anyone else who *wanted* to hear cars approaching could do so at the personal level… a little device on their hip would emit a tone when cars are detected… something like that… I realize that this isn’t a perfect, polished proposal, but I think it’s much more on the right track than just arbitrarily adding more noise to the world.

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  16. 16. billmill 6:02 pm 10/14/2009

    Tire noise is far louder than engine noise at speeds dangerous to pedestrians. That’s why the "perceptual psychologist" had to record the speed of his vehicles at five mph, to get a result which might get published.

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  17. 17. jckatz 6:38 pm 10/14/2009

    tharriss wrote: " we have to add expense"

    They are not adding expense, they are adding opportunity for marketing. The custom ring tone business turned into a $1-3 billion industry. This is from people that are only spending $0 to $200 for a device. If the automobile industry were to sell custom sounds, I doubt they will charge $0.99 a file. This will be HUGE!

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  18. 18. eddiequest 6:42 pm 10/14/2009

    LOL – "choosing your own noise"… yes, I can hear it now – RING TONES for cars.
    But seriously folks, I found the same kind of problem with my own E-car. It tends to scare the krap out of people when I come upon them. Now I just slow down a bit, and flip on the microphone, and say something like "VROOOM, VROOOM". ;)

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  19. 19. eddiequest 6:45 pm 10/14/2009

    Silly catfish – where’ve YOU been the last 8 years?

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  20. 20. eddiequest 6:46 pm 10/14/2009

    AWESOME idea, Mr.Tie. It’s a "horseful carriage". LOL

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  21. 21. bwilson4web 7:13 pm 10/14/2009

    We found the Prius fatality rate, 0.64 per 100 million miles, is less than half of the USA rates 1.37-1.51 per 100 million miles between 2001-07. So the first problem is we can’t find any "deadly." There are fatal Prius accidents including pedestrians.

    On July 1, 2009, a 97 year old pedestrian was struck and killed by a Prius. But he was under the I-290 overpass … ever been under an overpass … it is very loud from the overhead traffic. Sound obviously would not have worked but there are 4,500 pedestrians killed every year by sound emitting vehicles.

    We are already running the experiment with gas-only vehicles and we kill the population of a small town year after year. Making the Prius as noisy as these gas-only vehicles is repeating the same experiment and expecting a different result … the very definition of insanity.

    H.R. 734 and S. 841 legislate sound as the only solution. Pedestrian and accident avoidance systems like the SAAB, BMW and upper-end Toyotas will never be considered. Only the insanity of repeating the same experiment that kills too many pedestrians every year. It is legislating the pedestrian carnage we live with today.

    Robert J. Wilson, Huntsville, AL.

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  22. 22. Cliff Clark 8:03 pm 10/14/2009

    Deaf people like my 27 year old son have never heard the noisy cars. Somehow they manage not to get into more accidents than the average person. Perhaps people should just start paying more attention to what is going on around them. Anyone not capable of that is perhaps an excellent candidate for (un) natural selection.

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  23. 23. Cliff Clark 8:04 pm 10/14/2009

    Deaf people such as my 27 year old son have never heard the noisy cars, but seem to be able to avoid accidents. Perhaps people should just pay more attention to what is going on around them. Those that are not capable of doing so could perhaps be considered excellent candidates for (un) natural selection.

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  24. 24. danlock2 9:55 pm 10/14/2009

    *ahem* It’s more the drivers’ responsibility to avoid pedestrians; if driving laws are obeyed, drivers will be much more successful at avoiding the slower-moving pedestrians regardless of the volume of their automobile.

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  25. 25. Quasimodo 10:36 pm 10/14/2009

    The article’s chief concern is bladderflap and has much mold growing on it. It’s been around for years and should have died of old age by now.
    It’s been pointed out that tire-street interaction is one of the main noise making elements of street transport. Today’s cars are relatively silent, motor wise. Electric cars aren’t that much more quiet and their tires still make noise when rolling.
    In time the blind will get even neater gadgets than they have now. Technology is sneaking up on the whole blind problem just as it is on deafness.
    That said – I’d love a car with both unique sound options and active noise-neutralizing systems.

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  26. 26. ajft64 10:51 pm 10/14/2009

    Bicycles have been silent or nearly so for over a hundred years, this is nothing new. Ask any cyclist – and many motorists – and they’ll tell you endless tales of pedestrians who walk out in front of them. The "new" problem seems to be twofold:

    – pedestrians refuse to take responsibility for checking the road before crossing and will blindly step out from the kerb with their eyes buried in their cellphone and their ears plugged with their iPod headphones
    – motorists have little respect for anyone outside their protective metal box and do little to avoid collisions where they perceive that they are "in the right"

    The problem is people; people on foot won’t take responsibility for their actions and people in cars won’t take responsibility for theirs.

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  27. 27. sbearman 1:40 am 10/15/2009

    As a bicyclist, I have always relied on my ability to hear cars coming my way from behind. I have had a number of close calls with hybrids. The tire noise was not adequate to alert me, even when they were moving fast.

    I wonder if a relatively quiet sound could be directionally emitted from cars that was only audible for a certain distance in front of the cars. This would allow bikers and pedestrians both to hear hybrids coming without generating noise pollution for everyone else.

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  28. 28. mickep76 9:33 am 10/15/2009

    It doesn’t matter today’s pedestrians wear an iPod anyway.

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  29. 29. leggedfish 10:19 am 10/15/2009

    Newer internal combustion cars are nearly silent as it is. Think back and compare a normal (not giant SUV) car made within the past 10 years to what a car sounded like in the 1980′s. Using sound as a reliable distance measuring device for cars went away about 20 years ago.

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  30. 30. galaxy_man 11:55 am 10/15/2009

    OH NOES, pedestrians actually being forced to pay attention to their surroundings! We can’t have this kind of corruption in America! Get Congress to illegalize silent cars immediately!

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  31. 31. Deufox 1:17 pm 10/15/2009

    We have an opportunity here to reduce the amount of noise in the world. I think we should take advantage of it, rather than ruin the opportunity.

    People can learn to watch more carefully, using their eyes rather than their ears. They should be looking anyway.

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  32. 32. fb36 1:26 pm 10/15/2009

    Artificial noise should not be forced upon millions of people w/o asking them first!
    I think US government should look at public surveys at first before making it a law!

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  33. 33. sb1020 3:42 pm 10/15/2009

    I can understand that people see the electric cars quietness as a benefit, but say that one night a blind person is crossing the road, obviously he/she can’t see you, but in some circumstances, you can see them either, or if there is a sharp curb sometimes you cant stop in time. plus, the article said "The noise added to hybrids wouldn’t have to be particularly loud, Rosenblum said".

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  34. 34. galaxy_man 3:52 pm 10/15/2009

    A blind person crossing at night?

    Are there any other straws you want to grasp at? Take your time before giving us an answer.

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  35. 35. fb36 7:30 pm 10/15/2009

    Electric cars should make noise just like the other cars.
    They also must carry gas, burn it and make smoke too!
    Also if their weight is less than other cars then they must carry sand bags! :-)

    Also do not forget, when all cars make noise blind people easily walk around any city. People walking in the street also should make noises when there is any blind people around! :-)

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  36. 36. Johnay 10:55 pm 10/15/2009

    This reminds me of reading years ago about how active noise cancellation was going to replace mufflers (and give us all increased gas mileage by eliminating back-pressure in the exhaust.) Theoretically you could also substitute a different car’s sound, from a Model T to the Jetsons’ flying car, or anything in between.

    Whatever happened to that?

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  37. 37. mo98 11:10 pm 10/15/2009

    I’ve nearly been hit as a pedestrian by cyclists and been cut-off by drivers as a cyclist. Girls used to have bells and boys had horns attached to their bikes, In Europe many adult cyclists continue to warn pedestrians well in advance with a bell ring. At 5mph most coasting vehicles slipped into neutral will usually make no noise and infamously kill unsuspecting children. In reality there is little difference at higher speeds as tire noise exceeds most engine noise today. May I suggest a warning signal only if abnormal acceleration is attempted on an electric on a smooth dry surface, and some sort of motive hum otherwise on all others.

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  38. 38. Michael Hanlon 2:23 am 10/16/2009

    I am legally blind. I do not drive (only because of the cost of insurance)(Our states wiil take monies for licenses from anyone). I ride my bicycle. I installed an ‘A-ooo-ga’ horn on the handle bars. When I ride now, I just squeeze the bulb on the horn, a sound goes out and reflects off objects in my path and on the return my heightened bat hearing sense let’s me know if some unseen obstacle is in my way.

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  39. 39. JacobSilver 10:19 am 10/16/2009

    During the nineteenth century in New York City, during winter, the dominant conveyance was also noiseless, the sleigh. I guess, if you listened carefully, you might hear the horses breath. But city council acted, and required that all sleighs carry bells to warn pedestrians. It worked, and became the basis for at least one popular song. Bells may not be practicle with electric cars, but drivers are liable for watching out for people crossing their paths in cities.

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  40. 40. kenmarable 12:03 pm 10/16/2009

    I agree that quieter in general is better, but considering blind pedestrian’s some sort of noise is good.

    However, the study referenced isn’t real convincing. People only had 2 seconds to a hybrid car moving 5 MPH?!! Considering a brisk walking speed is probably 4 mph, it doesn’t sound like a real danger. Testing in the 15-25 mph range might actually be applicable to reality.

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  41. 41. Michael Hanlon 8:51 pm 10/16/2009

    I’m gonna get all my fellow blind poeple to get them thar licenses, buy them thar quiet cars and drive on them thar busy streets. Don’t worry though, We won’t be using the video capabilities of them thar cell phones. Oh, you don’t want us on your turf? Well don’t go making rules about how we’ll feel safe on our turf. Got that?
    Who’ll pay for the pedestrian equipment some of you suggest? I have a proposal: Do the actuarial math about how many blind people are going to die as a result of being hit by quiet cars, Arrive at a total payout of insurance costs to the heirs (a billion maybe?) and give it to us now while we can enjoy it and then we’ll be extra sure to ‘watch’ out at the curbs of America.

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  42. 42. Zhukova 9:45 am 10/18/2009

    Pedestrians should look both ways, but they have the same distractions as drivers: cell phones, friends, anxieties, etc. but the problem is not new, ie. horse and bicycle bells. Even ICE vehicles can be quiet enough in a parking lot to contribute to a pedestrian’s safety.

    The solution is to give cars the ability to recognize pedestrians with a video camera. Digital cameras already recognize faces easily and the technology is not expensive. Depending on the speed of the car, if a person is close to the road, the car could make a clicking sound like we hear at blind-pedestrian crosswalks.

    Legeslation that allows Harley Davidson or Mack truck ring tones for EVs is mindless and depressing, but I think better solution is possible.

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  43. 43. Michael Hanlon 8:17 pm 10/18/2009

    Right, when the facial recognition software spots the pair of sunglasses and adds the long cane into the image, the vehicle’s computer could send a speed up signal so’s the blind guy is for sure killed and the health care system wouldn’t have to expend money to care for a crippled blind guy. Win-Win.

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  44. 44. Michael Hanlon 3:48 am 10/21/2009

    Okay, no one else has asked it so I will. We all want to know who wrote the headline for this article. There is humor in it. I have wondered where Beavis and Butthead went when they left MTV. Now we know!

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  45. 45. raseclamid 4:19 am 10/21/2009

    As far as I know, humans can adjust to environment to a great degree. I agree to some people here that we are on transitional period to hybrid and electric cars. The sound of a rolling tires can take the place of an approaching gas engine sound. As our environment becomes less polluted by noise, we will become more adepth to the subtleties of noise around us. I had that experience when I live for 2 years in the rural areas. You will be amazed at how many sounds you could distinguished.

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  46. 46. Michael Hanlon 12:13 am 10/25/2009

    All the discussion here is about vehicles already in motion. What about the silent car just sitting there that all of a sudden begins to move? There’s no engine rev to alert you. There’s no tire/pvement/friction sound to alert you.
    A little pre-recorded vroom-vroom would come in handy in that situation.
    .Why just the other day, I was pedaling on the side walk on the left side of a road, safely removed ffrom the traffic by the curb ,a planting strip of grass and some of the sidewalk. Well, a car (I don’t think gender is pertinent but it was a woman) exited a Plaza parking lot, looking left the whole time to judge a merge into on-coming traffic. No chance presented itself and she , stopped continued to look left. I stopped my bike 1.5 feet away from her passenger door and waited. I couldn’t go in front of her ’cause of the traffic. I couldn’t go behind her ’cause she’d hugged the ramp side coming across the walk. So I sat (stood actually). I loudly said thanks for blocking the sidewalk and violating your stopline. No reaction. Noise had no effect on her. When her opening came, she turned her steering wheel for an even sharper right turn than she sat with and, as all you physicists know, the rear tires turn a tighter arc and she drove into my front tire. I yelled. She was even so close I banged on her trunk. She did not stop.
    Now lets put this event into the future with smart cars and my vision has finally decided to completely fail me not just 3/4 of the way. Her computer stops her car at the stop line before the sidewalk. I walk along tapping my cane and listening for any movement. Hearing none I proceed across the ramp area and her car quietly decides to go forward at the same time.
    . I know a lot of you will be happy this thorn is no longer around. But it’s not the way things should turn out if we are advancing and using technology to our benefit. In this case it seems we are using technology just because it exists. Don’t say that in Hiroshima.

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  47. 47. Ziggy 2:26 am 10/25/2009

    Now I’m glad a few have touched on this camera idea. Would it not be possible to have a string of LEDs across the dash that when the camera notices a child size to adult size object moveing towards the vehicle to light up that led to notify the driver that something is there. Aswell at that moment it could also send a sound out the horn something along the line (HELLO) loud enough to hear. I just don’t see why it is needed all the time. It could be fun once in a while but for me it would nice cruising in silence once in a while aswell… My two cents

    Brant

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  48. 48. Ziggy 2:41 am 10/25/2009

    Ultimitly it is the drivers responsibility I’ve had Actually to close calls and I’m sure neither were deaf. One was about to dart accross the road in front of the van that just pulled over in front of me and luckily I new there was no cars coming at me so I did what I could and few. The second rainy x-mas time of yr 2yrs ago a chick runs accross the in front I have to hit the brakes wheels lock up do what I can in that split second and again lucky. Now on to a funny point I pulled into work one night had a person calmly walk diagonally making wait longer then needed didn’t look up nothing and let’s just say I’ve got a 2.0L w/ cat cherrybomb then stainless pipe out to the side it sounds nice to me but I’m sure it’s anoying but it was the cheap thing 105 compared to 450 plus tax anyways an EV just makes so much sense they just need to make the good parts more available for us to do it ourselves. I for one will when I can.

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  49. 49. Michael Hanlon 1:34 am 10/28/2009

    An OBSERVATION: Throughout this discussion we have referenced the senses role in the driver/non-driver dilemna. I pointed out that even blind people can get licenses. They do test for vision. What sense that impacts driving ability does not get evaluated? Hearing! And this whole Blog is about.. wait for it.. sound and cars!!
    Imagine, if you will, ten years from now and that deaf person driving the car is unaware that the Vroom-Vroom isn’t working. That poses a threat to all, drivers and pedestrians.

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  50. 50. _mark 10:22 pm 08/13/2010

    i ride an electric bike and people here are in LA will just walk out in front of y0u without even looking. everyone here might as well be blind, they’ve all got their heads so far up their asses. pedestrians are hit here all the time by cars.

    Link to this

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