Cover Image: August 2008 Scientific American Magazine See Inside

Are Hybrid Cars Too Quiet to Be Safe for Pedestrians?

Pedestrians, used to loud engine noise, have less warning when a car powered by a hybrid or electric motor approaches















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Note: This article was originally printed with the title, "Didn't Hear it Coming".

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  1. 1. jjmrowe 05:24 AM 7/30/08

    buzzy hybrids: special hybrid noise possibly -- pretend ferrari or model T not a goof idea!

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  2. 2. ksgarvin 07:30 AM 7/30/08

    Please don't turn these wonderful cars into more excessively noise vehicles. We could use some quiet in the urban and suburban environment!

    A little sound, yes; I agree that being able to hear a vehicle is helpful. But it's not strictly necessary: deaf people manage to cross streets without benefit of hearing the traffic. Why? They LOOK. Remember from grade school? Look left, look right, look left. Do they teach this anymore?

    Seriously, don't go nuts putting beepers and strobe lights on the cars. They already do this to garbage trucks in my area and it's a distraction, not a safety tool.

    The bottom line is that pedestrians need to LOOK. And they need to turn down their music players once in awhile, too. Perhaps that is the real reason they can't hear the cars...

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  3. 3. candide08 09:00 AM 7/30/08

    Unless the Hybrid drivers are driving on the sidewalk pedestrians have no complaints. Simply LOOK before entering a street.

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  4. 4. Mark 12:57 PM 7/30/08

    Think of this as vehicular Darwinism. If you can't handle looking both ways before crossing the street the world won't miss you.

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  5. 5. clarissaP in reply to candide08 01:34 PM 7/30/08

    Cars often cross a sidewalk from behind a pedestrian on a sidewalk.
    It's how cars usually get off the street into a parking lot or residential driveway.

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  6. 6. nycsingletrack 02:57 PM 7/30/08

    "Pedestrian safety, he points out, is not a hybrid issue. Its a quiet car issue."

    Actually, pedestrian safety is a driver education issue AND a personal awareness issue.

    I commute by bicycle in NYC several times a week, and the pedestrians are unbelievable unaware of their surroundings. It's not the job of a motor vehicle to emit enough (annoying) noise to force your awareness.

    Despite being an avid motorcyclist, I think motor vehicles of any sort should be heard as little as possible. That goes for your weedwacker and leafblower too.

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  7. 7. seans_spam 09:57 AM 8/1/08

    Quiet cars would be really terrible; drivers and pedestrians would both have to watch where they're going! I hope we can keep the streets noisy so that we can stay accustomed to it.

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  8. 8. Doc Barnett 11:03 AM 8/1/08

    "Vehicular Darwinism" is a flattering way to describe one's misanthropic tendencies, but please consider that vehicles do not always have the right of way when they take "the way." It's common, actually, for us lower-life-form pedestrians to dodge out of the path of cars that have no business being where they are, and we can only do this if we HEAR them coming. I don't have eyes in the back of head to see a car turning into me after I've already "looked both ways" to cross with a walk sign. If you would rather run me down in this situation you will probably get away with it, but don't try to assuage your conscience in inapplicable concepts recalled from high school biology. (This is an argument against a laughing dismissal of accidental vehicular homicide more than against quiet cars. I agree with nycsingletrack that there is a lot more to pedestrian safety.)

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  9. 9. VancouverDave 11:08 AM 8/5/08

    When standing at a street corner, one does not hear a single car; rather, one hears dozens, if not hundreds of cars from all directions (not to mention the echoes of engine noise from building faces).
    Therefore, a silent car poses no additional risk as sound is not used to locate vehicles under normal circumstances. The "threat" of silent cars sounds (sorry) like the product of an over-anxious imagination.

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  10. 10. arleyl 01:32 PM 8/7/08

    A silent car does pose a risk. As a bicycle commuter on roads without bike lanes, I move closer to the shoulder when I hear a car approaching from behind. Around town, I rarely hear the Priuses, so I don't know to get out of their way.

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  11. 11. Ike 12:57 PM 8/9/08

    Has no one stopped to consider that ALL modern vehicle engines cannot be heard when they are cruising at city speeds? Try listening to traffic go by, and unless a vehicle is accelerating HARD (at which point, the Prius engine would also kick in), the only sound you hear is tire noise on the pavement, which, by the way, is a trait shared by Hybrid vehicles (they have tire noise, too). And, it seems that tire noise is enough to let ANYONE know that there is an oncoming vehicle. If someone gets hit at low speed by a hybrid vehicle, odds are the pedestrian was doing something wrong (like jay-walking), or, the driver was simply careless. Think about that before coming up with silly noise-producing devices that are NOT EVEN NEEDED!

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  12. 12. marcoramos 05:02 PM 8/13/08

    I don't like the idea of adding sound to quiet hybrids, but I'll do it if I can use the sound from the Jetsons' car.

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  13. 13. jr 08:23 PM 9/7/08

    We don't need louder vehicles. What we need is drivers that pay attention. I walk almost everywhere in Washington, DC. Even when pedestrians have the right away, drivers cruise through right-on-red-lights without even slowing down. Most are either talking on their cell phones or texting. Cars making a left turn provide a particularly severe hazard. They don't look before turning and find themselves with a pedestrian in front and and oncoming traffic on the side.

    What we need is a innovation that makes drivers pay attention. Not more noise for the streets.

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  14. 14. bwilson4web 06:07 AM 9/8/08

    The National Highway Traffic Safety Administration (NHTSA) hearing on June 23 covered this subject and the submissions are available at www.regulations.gov - search NHTSA-2008-0108. Looking at 5 years of NHTSA accident fatality data covering Prius operation: (1) the Prius has the same pedestrian accident rate; (2) 5 blind out of 4,700 pedestrians die each year, and; (3) the Prius has yet to kill a blind pedestrian. In 2006, 25 kids died in back-over accidents, crushed by rear bumpers and engine exhaust pipes.

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  15. 15. hscohen 05:21 PM 9/9/08

    This discussion would certainly be enriched by some solid research results on the best sounds to alert pedestrians and bicyclists to approaching cars. There's little point in discussing adding noise until we know what works.
    I do hope, though, that this issue won't foster a arms-race where everyone competes to be the most "noticeable" by emitting as much noise as possible.

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  16. 16. JAWermuth 05:41 PM 9/16/08

    Living in a quiet historic neighborhood in Rhode Island, we often come on people walking down the middle the street with our Prius. Often, they are talking on cell phones and paying no attention.
    A honk is too loud so I often open the window to announce the our presence.
    My wife and I have considered putting on a simple bicycle bell but there is no place to mount it on the aerodynamic body.

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  17. 17. arfc05 11:37 AM 10/11/08

    Why not require all vehicles to be hybrids? Can you imagine what the world would be like if it was quiet enough to hear birdsong on a city street?

    Adding noise to hybrid vehicles is insanity.

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  18. 18. Goran 12:37 PM 10/11/08

    We have the answer for the problem that visually impaired pedestrians have with hybrid and electric cars. P.A.S.S. allows the car to stay quiet, until a visually impaired pedestrian activates the system. The car then sounds a tone that the pedestrian can track. It also alerts the driver to the fact that there is someone in the area who cant see him and needs to hear him.

    and you can see it on youtube http://www.youtube.com/watch?v=FnWP38KzD3I thank you

    Goran Bogdanovic

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  19. 19. Texas Jim 12:56 PM 10/15/08

    For all you wiseguys wanting to thin the heard, I would like to to think of your children crossing the street, running in the street. And how about parking lots, when car backs up with seeing you and you have your back to it.

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  20. 20. Texas Jim 12:57 PM 10/15/08

    For all you wiseguys wanting to thin the herd, I would like to to think of your children crossing the street, running in the street. And how about parking lots, when car backs up with seeing you and you have your back to it.

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  21. 21. fedor1ht in reply to ksgarvin 11:04 AM 10/18/11

    If everybody all LOOK, then there won't be traffic accidents?

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