RIVERSIDE, CALIF.—People love their hybrid automobiles because, above all, they sip rather than guzzle now pricey gasoline. But as the owner of a standard minivan, I also covet a less touted benefit of electric engines: they are delightfully quiet.
So when I heard a graduate student say his group’s latest research suggests that hybrid gas-electric vehicles are too quiet, my ears perked up. He described his colleagues’ vision to equip these cars with sound-emitting devices to warn pedestrians. Were they planning to load a Toyota Prius with annoying beeps or the roar of a Maserati?
Certainly there seems to be some justification. In experiments led by perceptual psychologist Lawrence D. Rosenblum of the University of California, Riverside, blindfolded subjects who listened to recordings of cars approaching at five miles per hour could locate the familiar 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. And that was in the absence of traffic noise or other distractions.
In a second trial, Rosenblum added some realistic background noise to the recordings. My own appreciation of the safety issue stepped up dramatically when I experienced this scenario for myself: the Prius glided past me, undetected, time and again. By the rules of the game, I was hybrid roadkill 40 times over—as were the majority of Rosenblum’s formal subjects. In contrast, I correctly determined the approach direction of the Accord in all 40 attempts, from an average of 22 feet away.
Whether these laboratory results translate into the real world is unclear, from a scientific point of view. No concrete evidence proves that hybrid cars are involved in more pedestrian accidents than their noisier counterparts. And recent studies from Western Michigan University indicate that hybrids and conventional vehicles are equally safe when traveling more than about 20 miles per hour, because tire and wind noise generate most of the audible cues at those speeds. Hybrids also tested safe when leaving a stoplight; all Prius models in the study engaged their internal-combustion engines when accelerating from a standstill.
But many groups are not awaiting scientific certainty—or a death toll—to take action. Last November the Society of Automotive Engineers created a special committee to examine whether hybrid cars should be made more audible for the sake of pedestrians, particularly the blind. In April congressional lawmakers introduced a bill designed to tackle the same question, and the National Highway Traffic Safety Administration held a public hearing on the topic in June.
Adding noise to hybrids may be inevitable, but at least it won’t have to be loud, Rosenblum says. That good news stems from the human brain’s extreme sensitivity to approaching sounds relative to those that are fixed or moving away. Because they are more likely to pose a threat, approaching sounds most readily stimulate regions of the brain associated with motor action, he explains. Also, a large number of brain cells are specially attuned to sounds that get louder—which usually means they are drawing near.
So a warning can be subtle—as long as it’s the right kind of sound. Chirps, beeps and alarms are more distracting than useful, say Rosenblum and Everett Meyer of Enhanced Vehicle Acoustics in Santa Clara, Calif.; the best sounds for alerting pedestrians would be carlike—akin to the soft purr of an engine or the slow roll of tires across pavement.
Even with sound-emitting safety measures in the works, Robert S. Wall Emerson of Western Michigan University predicts a future of more tranquil transportation. Several high-end (and not so high end) gas-powered motor vehicles are already quieter than hybrids, he says. Ironically, in Wall Emerson’s most recent studies, hybrid SUVs turned up noisier than many internal-combustion vehicles. Pedestrian safety, he points out, is not a hybrid issue. It’s a quiet car issue.
See what we're tweeting about
21 Comments
Add Commentbuzzy hybrids: special hybrid noise possibly -- pretend ferrari or model T not a goof idea!
Reply | Report Abuse | Link to thisPlease don't turn these wonderful cars into more excessively noise vehicles. We could use some quiet in the urban and suburban environment!
Reply | Report Abuse | Link to thisA 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...
Unless the Hybrid drivers are driving on the sidewalk pedestrians have no complaints. Simply LOOK before entering a street.
Reply | Report Abuse | Link to thisThink of this as vehicular Darwinism. If you can't handle looking both ways before crossing the street the world won't miss you.
Reply | Report Abuse | Link to thisCars often cross a sidewalk from behind a pedestrian on a sidewalk.
Reply | Report Abuse | Link to thisIt's how cars usually get off the street into a parking lot or residential driveway.
"Pedestrian safety, he points out, is not a hybrid issue. Its a quiet car issue."
Reply | Report Abuse | Link to thisActually, 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.
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.
Reply | Report Abuse | Link to this"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.)
Reply | Report Abuse | Link to thisWhen 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).
Reply | Report Abuse | Link to thisTherefore, 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.
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.
Reply | Report Abuse | Link to thisHas 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!
Reply | Report Abuse | Link to thisI 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.
Reply | Report Abuse | Link to thisWe 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.
Reply | Report Abuse | Link to thisWhat we need is a innovation that makes drivers pay attention. Not more noise for the streets.
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.
Reply | Report Abuse | Link to thisThis 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.
Reply | Report Abuse | Link to thisI 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.
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.
Reply | Report Abuse | Link to thisA 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.
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?
Reply | Report Abuse | Link to thisAdding noise to hybrid vehicles is insanity.
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.
Reply | Report Abuse | Link to thisand you can see it on youtube http://www.youtube.com/watch?v=FnWP38KzD3I thank you
Goran Bogdanovic
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.
Reply | Report Abuse | Link to thisFor 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.
Reply | Report Abuse | Link to thisIf everybody all LOOK, then there won't be traffic accidents?
Reply | Report Abuse | Link to this