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Sounds For Silent EVs: Solving a Problem That May Not Exist

 
32 10,347 views July 23, 2010

A new study concludes that Prius repairs cost 8.4 percent more than repairs on non-hybrid economy cars.

A new study concludes that Prius repairs cost 8.4 percent more than repairs on non-hybrid economy cars.

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It's a wonderful TV news flash: Blind people in peril from killer electric cars! News at 11. The fear is that electric vehicles are so silent that blind people can't hear them coming, so new draft safety regulations may now require electric vehicles to emit sounds.

There's just one problem: Accident data from the National Highway Traffic Safety Administration show no increase in deaths for blind people in pedestrian accidents during the 10 years that hybrid-electric vehicles have been sold.

Full hybrids, including the definitive 2010 Toyota Prius, are a proxy for EVs because they can operate in full electric mode at low speeds. With the gasoline engine off, the only sounds they emit are tire noise plus a slight whine from the electric motor.

Pedestrian Fatalities, 1994-2008, from NHTSA Fatality Reporting System data

Pedestrian Fatalities, 1994-2008, from NHTSA Fatality Reporting System data

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Early data showed problem

Preliminary data seemed to show that hybrids were more likely to be involved in pedestrian crashes or hit cyclists. An NHTSA report issued last November aggregated accident reports from certain states.

It concluded that hybrids like the Toyota Prius were involved in pedestrian crashes at a rate of 0.9 percent, half again as high as the 0.6 percent rate for gasoline vehicles. Hybrids were also twice as likely to have hit cyclists, at a rate of 0.6 percent versus 0.3 percent.

To its credit, that report noted its own methodological weaknesses. Only 12 states record vehicle identification numbers (VINs) of cars involved in accidents, allowing hybrids to be distinguished from gasoline cars. And only accident data from 2000 or later was used, cutting the size of the sample set.

A more comprehensive look

But now EV enthusiast Mark Larsen (he's also an Emeritus Professor of Spanish at Utah State University) has analyzed some additional data. He used 1994-2008 figures from the Fatality Reporting System maintained by the NHTSA.

If silent hybrid vehicles posed a threat to pedestrians, he reasoned, then the number of pedestrian deaths should have risen since 2000, when the first hybrids were sold. There are now roughly 1 million hybrid-electric vehicles among the 300 million on U.S. roads.

But in fact, despite increasing numbers of hybrids on the roads, the rate of pedestrian fatalities has in fact fallen over that same period.

Total Traffic Fatalities, 1994-2008, from NHTSA Fatality Reporting System data

Total Traffic Fatalities, 1994-2008, from NHTSA Fatality Reporting System data

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Next up, please: Injuries

We like Larsen's analysis, but we would observe that it has two problems. First, it doesn't factor in Vehicle Miles Traveled, which is  correlated with a fall in accident deaths. The rate of deaths per VMT has declined for decades, as cars come with more crash safety equipment.

Second, Larsen really only addresses half the issue. Fatalities from accidents are one data point, but injuries would be another--and are far more common than deaths.

Since hybrids and electric vehicles are at their quietest at low speeds--below 15 miles per hour, say--we'd suggest that if there is a danger from silent vehicles, it would be reflected not in deaths but in injuries.

Larsen nods to this by noting that throughout the study period, not a single blind pedestrian was killed by a vehicle traveling at less than 20 miles per hour. His report is silent, however, on non-fatal injuries that may have been suffered by blind pedestrians.

We eagerly await the arrival of someone's analysis of injury data along the same lines as Larsen's fatalities study.






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Comments (32)

  1. By  Bob Wilson Posted: 7/23/2010 7:48am PDT

    About Larson's study, ". . . it doesn't factor in Vehicle Miles Traveled, which is correlated with a fall in accident deaths." I did a similar study for the Prius years 2001-07 (see URL on my name) and used the annual Prius sales and 15,000 miles per year the mileage EPA uses for fuel costs, and calculated the fatality rate per 100 million miles . . . the same units the NHTSA uses in their annual report.
    Our data shows the Prius has half the fatality rate the NHTSA reported for all USA vehicles over the same years including the pedestrian fatality rate.
    I notice you don't ask that the flawed NHTSA report, DOT HS 811 204, also "factor in Vehicle Miles Traveled". That flawed NHTSA report did not count the vehicles in the 12 States during the study.
    Bob Wilson, Huntsville, AL
     
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  2. By  Bob Wilson Posted: 7/23/2010 8:14am PDT

    One correction, the legislation forces the noise maker to be on all the time. The Volt and earlier EV1 made the noise optional, under driver control.
    By the legislation, when someone is driving into their driveway in the middle of the night, the neighbors will enjoy the legislated, mandatory noise. When the driver is in a nature sanctuary, the mandatory noise will be there. When road converge at a stop light, the legislated noise will be there to mask each other ... as engine noise does today.
    The "Noise Pollution Clearinghouse", 1-888-200-8332, has already pointed out that more noise simply hides deadly cars 'in the racket' as it already does today. Their record is available at www.regulations.gov, search NHTSA-2008-0108 as well as other position papers.
    Bob Wilson, Huntsville, AL
     
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  3. By  paul wallich Posted: 7/23/2010 9:13am PDT

    As usual, such vague legislation is even worse than you might think. Our ability to localize sounds depends on frequency, so you could easily put a blind person in the position of knowing there are cars somewhere in the vicinity, but no idea where or how close.
    And depending on the manufacturer to sort things like this out is not such a good idea: consider, for example, the prius backup alarm, which is pretty much only audible inside the vehicle.
     
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  4. By Colby Posted: 7/23/2010 10:09am PDT

    Everyone is blind to a car approaching from behind. All cars are silent when you're wearing your iPod. It is ultimately up to the driver to operate their vehicle in a safe manner, at any speed and noise level.
     
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  5. By  evchels Posted: 7/23/2010 10:14am PDT

    Nice piece John, as always! To counter one point though, I don't think the issue is a flaw in Mark's logic so much as lack of available information to defend this legislation. We do need data on injuries, yes. And while many of us suspect that adding noise to cars (at least in a passive, constant manner) is not the right solution, data before legislating is exactly what we've been asking for all along. Thank you for illustrating our point so well!
     
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  6. By  Tom M Posted: 7/23/2010 10:40am PDT

    I'm one of the MINI-E trial lease participants and recently asked a BMW representative if any of the 600 MINI-E's were involved in a pedestrian accident this year. The answer was no. These cars logged nearly 4,000,000 miles this year and there wasn't one incident where one hit a pedestrian. I know this is a small sample, but it further proves that we need more conclusive data before we start making laws. What's the rush? It's going to take a few years before these cars are on the road in any real substantial numbers. Why has this been seemingly fast-tracked? Who's REALLY behind this push to quickly legislate?
     
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  7. By  Bob Wilson Posted: 7/23/2010 11:58am PDT

    Obviously the blind advocacy groups but they have a partner, Dave McCurdy of the Auto Alliance. Hybrid sales are about 2-3% of the USA sales so the other 97-98% are engine only powered vehicles. But making engine vehicles quieter is a hard engineering problem that becomes a lot easier if there is a 'noise floor.' This legislation caps how quiet gas and diesel engined cars have to be. . . . Of course the Auto Alliance may be totally committed to blind pedestrian safety . . . and pedestrian safety too like the EU pedestrian safety standards are needed in the USA too.
    The real answer is are you going to keep quiet too or call your congress critters about H.R. 5381 and S. 3302, "Motor Vehicle Safety Act of 2010" and oppose the car noise standard?
    Bob Wilson, Huntsville AL
     
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  8. By wintermane Posted: 7/23/2010 12:02pm PDT

    As someone who is legaly blind and was nearly hit by a hybrid suv I can say.. Go ahead close your eyes... Now try and get around with the idiots that drive now adays driving silent cars... Feel lucky? I dont anymore I got my get out of death dree pass all used up now.
     
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  9. By Tom Betz Posted: 7/23/2010 12:11pm PDT

    What about bicyclists? Most engage all their senses while riding. I wonder if empirical data exists regarding hybrid/bike encounters at slow speed?
     
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  10. By John Knoll Posted: 7/23/2010 1:15pm PDT

    It's idiotic to damage one of the very nice things about electric cars - their quietness - because someone thinks it might be a problem for a small minority. Why not invert the problem and create devices that can detect approaching electric cars (via the magnetic fields they emit, or ultrasound, or bluetooth, etc.) and emit a sound for the carrier of the device? That way only those with a desire to hear the noise need hear it.
     
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  11. By Bob Wilson Posted: 7/23/2010 1:46pm PDT

    Hi John Knoll. The EV1 and Volt both have operator enabled noise makers. I understand the Leaf is also driver operated. But the law takes those controls away. The sad thing is there is a reasonable compromise, putting those turn signal light relays co-located with lights for all cars and require backup lights to flash via a clicking relay. But the blind "won't hear it."
    Now "wintermane" is it true you've never been almost hit by a gas car? Have you tried getting a dog? The seeing-eye dog assistance schools bought Prius years ago and train the dogs and clients to deal with hybrids.
    Bob Wilson, Huntsville AL
     
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  12. fb_1001015277 avatar John Briggs Posted: 7/23/2010 2:39pm PDT

    Take the conversation away from EVs for a moment and think about bicycles and pedestrians for a moment. Sometimes bicycles and pedestrians use the same pathways and it can make for dangerous situations.
    I have been commuting on a bicycle in Boston lately and have to be very diligent to not run down pedestrians. They tend to be slightly clueless to the fact that they are sharing the pathway. Sudden sideways movements are comment and tired runners especially prone to erratic movements.
    So as a bicyclist, what should you do. I have seen several techniques.
    1) Ignore the pedestrian and barrel through.
    2) Yell, on your left just prior to passing
    3) Ring a bell, just prior to passing
    4) Only pass pedestrians at low speeds.
    I have adopted #4. For the guys ringing the bells, passing me, I frequently cannot locate the source of the sound. It might be behind me or in front of me. It does not seem to be helpful. Yelling sometimes scares people and they move in the wrong direction. Sadly, slow careful bicycling seems to be the only answer.
     
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  13. fb_517473963 avatar Brian Yennie Posted: 7/23/2010 4:36pm PDT

    "If silent hybrid vehicles posed a threat to pedestrians, he reasoned, then the number of pedestrian deaths should have risen since 2000, when the first hybrids were sold. There are now roughly 1 million hybrid-electric vehicles among the 300 million on U.S. roads."
    How exactly was he expecting 1 in 300 cars (and less than that over the whole period) to show a statistically significant effect? These numbers fluctuate by whole percentage points already due to other factors. Not to mention that blind pedestrians are also a small fraction of all pedestrians.
    Might want to put a statistician on this, not a spanish professor...
     
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  14. fb_1510606196 avatar Carl Thelin Posted: 7/23/2010 6:31pm PDT

    Hey guys - what about people who can't hear at all, or like me - very hard of hearing since birth? When riding a bicycle or walking, I need to be very careful about cars, or other bikes, coming from behind. I'm 80 years old and never been hit. Why? "Defensive Walking" I suppose. Good for everyone. Don't expect gov't to take care of you.
     
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  15. fb_1510606196 avatar Carl Thelin Posted: 7/23/2010 6:37pm PDT

    I think the other reader made an excellent point. If you know statistics at all, you realize that the sample side of vehicles and blind persons and injuries reported is much too small to be make me confident of the analysis
     
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  16. By Robert Chin Posted: 7/23/2010 8:14pm PDT

    How much of the increase in pedestrian safety is due to additional regulations passed in the last decade in Europe? My understanding is that a number of additional regulations were made in order to increase pedestrian safety in an accident 25 mph and under. It's likely that these changes made in vehicle design impacted pedestrian safety in the US given that many car designs are shipped worldwide. Just because cars have gotten safer overall for pedestrians doesn't have any bearing on whether EVs are safer for pedestrians or not.
     
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  17. By Marc Posted: 7/23/2010 8:43pm PDT

    The over all rate of all vehicle accidents is going down but cell phone use in cars is going up so cell phones make us safer? I don't think so. It's flawed reasoning to suggest that because there is no increase in blind people being in accidents that hybrids are not a problem. If there were no hybrids then maybe the rate would have gone even lower.
    Number of mile driven means nothing. There aren't pedestrians on the highways, usually, so all those miles would have to be thrown out. What info is there that lets you control for that? I don't see a way to make that info useful. So you have to just rely on number of vehicles pedestrian accidents and what kind of cars are involved. The rate of hybrid accidents may be higher because they spend more time on local city roads than the same number of conventional cars. Again if there were no hybrids the rate could be even lower. You just don't have the info to make the statements that hybrids are or are not worse for pedestrians.
    It does seem reasonable that silent cars would cause more problems for pedestrians that's just guessing but it's really all we got. And I'm not sure I want my car to be so silent I wouldn't hear it being taken out of my drive way at 2 am by my teenager.
     
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  18. By KD Posted: 7/23/2010 8:51pm PDT

    If this legislation passes, in 50 years or so, people will be using it as examples of reactionary lawmakers, just as we look back on those lawmakers who, in the early days of the automobile, passed laws requiring cars to have people going ahead of them with lanterns and flags.
    Idiots.
     
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  19. By Marc Posted: 7/23/2010 10:31pm PDT

    How is it nobody is pointing out the obvious hole in this study? That is to say: in spite of the fact that OVERALL accidents are going down, the percentage of accidents caused by EVs is higher than non-EVs -- and when you consider that EVs still make up a very minor portion of the vehicles on the road, that's a pretty disturbing trend.
     
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  20. By Neil Posted: 7/24/2010 5:19am PDT

    I dad was blind and could hear lamp posts buzzing from 100 yards....!
     
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  21. By Mark D Larsen Posted: 7/24/2010 9:03am PDT

    Brian Yennie: despite your snarky tone, you make a valid point: I am NOT a statistician by any stretch of the slide rule: my professional expertise is in languages, literature, and culture. I merely extracted what information I could find on the issue from the FARS system because, after sending repeated requests for pertinent data to the NHTSA, our legislators, the National Federation of the Blind, and even Nissan, nobody has yet to provide any conclusive statistics that prove beyond doubt the need for such a "noise" regulation. I take it that you ARE a statistician, and could produce those data for us. Please do!!! We should always have solid empirical evidence to substantiate the need for such a law before enacting it --and not just theory or anecdote.
     
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  22. By  Bob Wilson Posted: 7/24/2010 11:04am PDT

    Marc posted,"the percentage of accidents caused by EVs is higher than non-EVs" which is wrong. The report, DOT HS 811 204 should be downloaded and read. Table 6a reports "19" turning and "7" backing accidents for all hybrids in 12 states from 2001-07 and this is claimed to be twice the rate of turning and backing accidents. However, there was a significant reduction in 'straight line" accidents, ~119 incidents, that did not happen.
    This NHTSA does not claim a doubling of hybrid risks but Cherry picked just turning and backing, a small fraction of all accidents. The authors ignored the elephant in the room, straight line accidents.
    Download and read the report and then call you Congress critters to complain about the noise amendments to H.R. 5381 and S. 3302. Your silence now will be busted in the future.
     
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  23. fb_517473963 avatar Brian Yennie Posted: 7/25/2010 1:13am PDT

    Mark: my snark was perhaps misdirected. Kudos to you for approaching the issue regardless of your particular expertise. I simply feel it is unfortunate that this article confounds the issue by still missing that the original hypothesis (that we should see an increase in total fatalities) is off-base.
    The type of data that could really show this would have a control group -- i.e. a population of blind people that does *not* encounter hybrid cars compared to an otherwise identical group which *does*. Or at least some correlation -- like blind pedestrians getting hit twice as much in a state where there are a lot of hybrids on the road.
    That said, one could argue that we should err on the side of caution if we can't prove it either way... certainly even reasonable doubt can be used if lives are at stake? And then there's defining "reasonable" ...
     
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  24. By Matt Posted: 7/25/2010 4:10am PDT

    As someone who live near a main road, one of the benefits I look forward to with electric vehicles, is a reduction in road noise.
    Noise pollution is linked to poor health, stress (eg heart disease) and sleep problems. The latter is in turn linked to many road and industrial accidents.
    Intentionally making cars louder than they need to be could likely kill many more people that it would save.
     
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  25. By Walter Lee Posted: 7/25/2010 5:51am PDT

    The sloping frontal area of the Insight,Prius, Civic, Fusion hybrid is more likely to injure than kill a pedestrian or cyclist in a frontal collision - especially at lower speeds that the electric motor. A vertical frontal area like a Chrysler RAM pickup is likely to kill a pedestrian or cyclist in a frontal collision. My hunch is that hybrids tend to be driven more miles than a conventional gas powered vehicles so the reason they were gettin into more accidents in the limited initial study was because these hybrids were being driven 50% MORE OFTEN - hence their risk for accidents went up 50%. Since EVs have limited range my hunch is that they won't be driven as much as a conventional gasoline vehicle so the risk should drop. Speeding, driver fatigue, and cell phone usage are the main causes of accidents in MD-VA-DC.
     
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  26. fb_1591302611 avatar fb_1591302611 Posted: 7/26/2010 4:46am PDT

    Folks should check their facts and data by reading the NHTSA report, DOT HS 811 204, that can be downloaded from their web site. Walter Lee, the report did not count the number of hybrids and non-hybrids in the 12 state study . . . read the report. Speculation of injury vs fatalities is best handled by getting and comparing Fatal Accident Reporting System (FARS) data with the same 12 state injury data but this was not done.
    Fact based, accident analysis should be used instead of this biased and incomplete report. By ignoring the 4,300 dead pedestrians last year for this 'ear wash,' we are condemning another 4,000 to death by auto.
    Bob Wilson, Huntsville AL
     
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  27. fb_1591302611 avatar fb_1591302611 Posted: 7/26/2010 5:40am PDT

    Using the NHTSA report and annual Toyota sales of the Prius and Corolla, the cars primarily used in the NHTSA report. Using the 2001 and 2007 sales, the Corolla was ~75% yet accounted for 98% of the pedestrian accidents. The Prius was ~25% yet accounted for only 2% of the pedestrian accidents. Source data, Wiki annual sales Prius, Corolla, and accidents from NHTSA DOT HS 811 204, Table 2.
    The advocates of this law are giving the Corolla a free pass to kill pedestrians at a rate several times that of the Prius.
    Bob Wilson, Huntsville AL
     
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  28. By Mark D Larsen Posted: 7/26/2010 6:24pm PDT

    "We should err on the side of caution if we can't prove it either way."
    No necessarily. There is a safety "threshold" that society will accept. We KNOW that seat belts save lives. Why, then, don't we mandate that they be worn on buses, streetcars, shuttles, subways, trains? Because to the general public the hassle just isn't worth saving a few more lives. A sad reality, but true.
    This is also the case with the noise issue. Let's say that a study proves that EVs/hybrids are causing more blind fatalities. To save those lives, shall we add vehicle noise wherever there are intersections, parking garages, toll booths, speed bumps, school zones, driveways, roundabouts, parking lots --even though there isn't a blind person within earshot?
    I don't think society would accept that "threshold." Especially as the number of EVS/hybrids grows to the point that there are several at such places.
     
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  29. By Jason Terryn Posted: 11/30/2010 1:28pm PST

    I agree that we shouldn’t expect government to take care of us. I’m blind and I try my best to be careful and alert – we can’t be reckless and then blame other people when we get hit – I want to take care of my part of the equation. And I also agree that this legislation might be hasty. I mean, next thing we’ll be making laws prohibiting driving if you’ve gotten less than eight hours of sleep the night before! These are matters of personal responsibility – on both sides, though. But one big step towards such personal responsibility in drivers will only happen when they actually do start to care about the plight of blind pedestrians. Then they might take precautions to drive more carefully, be more alert, and – yes – want to drive automobiles that don’t pose a risk to anyone’s safety. I don’t much like the careless attitude ya’ll seem to have about blind pedestrians in general. It’s so easy to dismiss someone when you haven’t ‘walked in his shoes’. Must there be fatalities before anyone pays attention? Two people I know were hit this summer. No deaths but serious injuries. One was blind and the other was a sighted bicyclist. If individuals actually took responsibility and cared enough not to want to endanger people in this way then the government wouldn’t have to make laws like this. Freedom ends where personal responsibility ends. The government is forced to step in when people get selfish and lazy and won’t make responsible decisions themselves.
     
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  30. By Jason Terryn Posted: 11/30/2010 1:30pm PST

    ....I don’t much like the careless attitude ya’ll seem to have about blind pedestrians in general. It’s so easy to dismiss someone when you haven’t ‘walked in his shoes’. Must there be fatalities before anyone pays attention? Two people I know were hit this summer. No deaths but serious injuries. One was blind and the other was a sighted bicyclist. If individuals actually took responsibility and cared enough not to want to endanger people in this way then the government wouldn’t have to make laws like this. Freedom ends where personal responsibility ends. The government is forced to step in when people get selfish and lazy and won’t make responsible decisions themselves.
     
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  31. By Jason Terryn Posted: 11/30/2010 1:30pm PST

    Matt - the kind of noise levels necessary to alert a blind person to an approaching car are not going to be loud enough to cause serious noise pollution any more than your dishwasher probably does. And honestly, there are several million blind people in the US at risk of being mowed down by a hybrid auto; probably a smaller percentage of people actually suffer life-threatening harm from noise pollution.
     
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  32. By Bob Wilson Posted: 12/14/2010 2:00am PST

    Jason - folks are sympathetic to the blind, access problem but not to noise generators that fail to reduce owner or other pedestrian risks. In contrast, the Cameron Gulbransen Kids Transportation Safety Act is moving into final rules that will put backup cameras on all cars (NHTSA-2010-0162-0002.pdf.) I read a claim that it would be cheaper to 'just add backup noise generator' while ignoring the documented exhaust pipes under the rear bumpers in the accident reports. Worse, kids, 2-5 years old would have to be 'trained' to understand that this additional noise is a hazard. But universal backup cameras work for kids, the blind, and a building post I once backed into. It solves a documented, fatality involved, safety problem with at least 100 fatalities projected to be avoided each year. Noise generators are not even within an order of magnitude in projected safety improvement. - Bob Wilson, Huntsville, AL
     
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