Archive for the ‘Drivers’ Category

The Ahem Signal

Reader Jesse asks a question about a situation that occurs regularly in traffic:

I saw a car today stuck behind an SUV. The car wanted to turn right at a red light, but the SUV was sitting there waiting for the green.

It was obvious that the car wanted to turn right, he had his signal on, he would creep up a few inches every now and then, and he was making moves to creep by the SUV, but did not have enough room. And I thought, I’m sure if the driver of the car could politely ask to get by the SUV would let him. But with his other methods of communicating failing (turn signal, creeping), the only thing left would be honking.

Honking is pushy. I thought, what if there were other audible signals? Something less pushy that sounded more like an ‘excuse me’ than a “HEY!” Has anything like that been attempted or marketed?

While I know of other alternative signaling systems that have been tried, I’m not aware of anything on this order. Of course, with existing horns, there’s a certain range of expression — the quick tap generally means something different, or is expressed differently at least — than the long blast.

But it is difficult to send a precise message with a horn, and if the person doesn’t understand what they are being asked to do, confusion and perhaps hostility will ensue. One reason this sort of thing is easier dealt with outside the car is that we can gesture with our eyes – we have white sclera in our eyes precisely for this reason, some have theorized — and indicate what we are asking of a person and boost the chances for cooperation.

This raises another point; in New York City, as no doubt elsewhere, we could use a quieter, secondary horn — sort of an “ahem signal” — for reminding people to move when the light has turned green. Sure, there’s the headlight flash option, but that assumes the driver ahead is looking in the rear-view mirror. Of course, when I see the person ahead is on a phone, the loud blast comes in quite handy.

Posted on Friday, April 24th, 2009 at 4:33 pm by: Tom Vanderbilt
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Does a Forward-Facing Bike Light Increase Rear Visibility?

A driver has been exonerated in Australia for striking a cyclist because he did not have a front-facing light and was, in the words of the magistrate, “an accident waiting to happen.” There’s just one thing: He was struck from behind, and he was sporting a rear tail-light.

Police prosecutor Sergeant Bob Anderson submitted that a headlight was not relevant because Mr Angel was hit from behind.

He said if Mr Angel was found to be wearing the yellow jacket, there would have been sufficient reflective material clearly visible by cars.

“A flashing red light was displayed on the victim as required by the road rule,” Sgt Anderson said.

So far, so good.

Defence lawyer Jon Irwin submitted that a cyclist riding in darkness required a headlight, rear light and reflectors on the bike.

After hearing six prosecution witnesses and two defence counsel witnesses, Magistrate Terry Wilson found Mr Angel failed to equip his bike with the requirements.

“If he had a (front) light it would have projected 200m in front and Ms Jasper could have picked up a bike was on the road,” Mr Wilson said.

This I find a bit hard to swallow. Firstly, I can’t say I ever spotted a cyclist from behind by dint of their front light. Secondly, maybe I’m using the wrong light, but there’s no way the beam projects 200 meters — it spills a (very) little light on the pavement about 15 feet of me. But maybe others out there have had a different experience?

(Horn honk to Treadly)

Posted on Thursday, April 23rd, 2009 at 7:04 am by: Tom Vanderbilt
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Feet on the Dashboard

The warmer weather this past weekend brought out a summer car ritual, one that admittedly is on my large list of car-culture pet peeves — things like stuffed animals in the rear-window ledge, or vocoder-heavy R&B (can we call for a moratorium on this device, please?) played at top decibel on my street.

I’m talking about feet on the dashboard. OK, yeah, call me uptight, neurotic, etc., but I tend to be rather repulsed by the site of bare feet in a public environment that isn’t the beach. Maybe it was those hacky-sack players on the quad in college. In business class to New Delhi I had to gently rebuke the passenger behind me, a kindly businessman who nevertheless saw fit to rest his unadorned foot on my armrest, just behind my elbow. The profusion of “mandals” leaves me cold.

But with alarming frequency one will spy, in the neighboring lane, a pair of bare feet propped up on the dashboard, or even dangling out the window (of the passenger side, of course; when you see this on the driver’s side, it brings up a whole other level of concerns). The phenomenon seems to tilt, demographically, towards a male driver and a female passenger. Again, call me uptight, but if there’s one thing I don’t want on my car’s interior surfaces it’s the oils, exfoliated skin, fungal detritus, etc., of someone’s feet. But the real issue, of course, is airbag deployment. When activated, airbags burst forth at around 200 MPH (and remember, you’ll be going forward), with tremendous loads that get higher the closer one is to the airbag. According to one study:

For example, at a distance of four inches from the airbag face to the chest plate, the deploying airbag exerted a maximum load of 912 pounds when released. In the slow motion video clip captured by Dr. Kowalski’s high speed camera, one can clearly see the chest plate on the fixture bow upward as the airbag pushes against it.

It doesn’t take a rocket scientist to picture what would happen to one’s legs if driven forward at such speeds and loads by an airbag; I don’t have statistics, but there must be numbers on injuries caused by airbags due to non-standard seating arrangements, or some such.

I looked in my copy of Accidental Injury: Biomechanics and Prevention, by Alan M. Hanum and John W. Melvin, but found nothing on the subject of airbags and feet. I did find, however, this rather sobering passage: “A laboratory study by Lau et al (1993) examined the potential for injury from out-of-position anesthetized swine with deploying driver airbags… splenic lacerations were the most frequent abdominal injury, often extending through the thickness of the spleen.”

It’s not a direct comparison, but extrapolating from this it seems like nothing good is going to happen if a crash were to occur and your feet were propped up at eye level — whether you were wearing shoes or not.

Posted on Monday, April 20th, 2009 at 11:40 am by: Tom Vanderbilt
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‘Portion Distortion’ and the American Road

I’ve recently been reading a number of papers by Brian Wansink, director of the Cornell Food and Brand Lab at Cornell University, and author of Mindless Eating.

One of Wansink’s more interesting findings is that the way food is served to us affects how much of it we will eat. He calls this “portion distortion.” Not only does the size of the portion itself affect how much we will eat, but so too does the size of the container it comes on (or in).

This seems to happen even to highly educated health professionals; in one study, he found they ate 31% more ice cream when it was served to them in a larger bowl (with a larger spoon, their consumption went up by more than 12%). In another experiment, people given larger containers of popcorn in a theater ate more than those given smaller containers — even when the popcorn was stale (though the affect was reduced when the popcorn wasn’t fresh — i.e. larger containers boosted consumption by 45.3% with fresh popcorn, and by 33.6% when it was stale). This effect typically seems to happen without people being aware of it.

It’s not difficult to imagine the public health consequences of this, particularly as the American obesity epidemic seems to roughly track a number of changes Wansink has identified in portion size. To wit:

We find portion distortions in supermarkets, where the number of larger sizes has increased 10-fold between 1970 and 2000. We find portion distortions in restaurants, where the jumbo-sized portions are consistently 250% larger than the regular portion. We even find portion distortions in our homes, where the sizes of our bowls and glasses have steadily increased and where the surface area of the averaged dinner plate has increased 36% since 1960. And if our bowls, glasses, and plates do not distort us, our recipes will. In the 2006 edition of the Joy of Cooking, the serving size of some entrées has increased by as much as 62% from some recipes in the first edition of 1920.

One problem (there are others), Wansink suggests, is that the feedback loops begin to fray with larger portion size: The larger the portion size, the less accurate the estimation of calories consumed becomes.

What does this have to do with the road? There is an interesting story in how the rise in portion size — often associated (as Wansink notes) with fast-food restaurants — historically tracks the huge increase in miles traveled (183% growth in per-person miles from 1969 to 2000, a period in which the number of persons itself increased only 41%), which itself is associated with the rise of those same restaurants; not to mention the much-debated work linking obesity to density and travel modes.

But I had a different comparison in mind: The way the size of our roads affects our behavior in “consuming” them as drivers. This was brought home to me again in a recent video made by a group called Park Slope Neighbors, which is working to reduce the size of streets like Brooklyn’s Prospect Park West (a five-lane thoroughfare, two lanes of which are dedicated to parking). As the video below shows, the speeds on the street are routinely in excess of the 30 MPH limit. What makes this particularly worrisome is that across PPW lies Prospect Park itself, and there is thus a steady march of pedestrians (including many children). I’m often struck as a driver by how many people are blowing past me; and, just from personal experience, I see more red-light running on this street than others in NYC.

The one thing I rarely see on PPW is the street used to its full capacity by cars. So in the 90% of the time it’s not hitting that full peak (my own wildly rough estimate, NYC DOT, please feel free to weigh in with actual numbers!), it is treated more like an urban highway, with speeds of 45 (or higher) mph not uncommon.

When I took my U.K. driver’s test in the suburb of Pinner, near London, I was intrigued by how, on several local roads, I often had to pull over to let another driver past, so narrow were the residential streets. This is something I can’t remember ever having had to do at home. In the U.S., talk of narrowing roads often leads to the reflexive question “What about emergency response?” Somehow, England manages to have these roads without suffering from a rash of people dying in house fires (needless to say their traffic safety record is better as well; as a friend who did some consulting for the Department for Transport recently told me, somewhat amazed, ‘they actually seem to really care about reducing the number of people killed on the roads’).

One of the recommendations for Prospect Park West is to put it on a “road diet,” a deeply suggestive phrase in light of Wansink’s research. A separated bike lane would be a great place to start — and would reduce the frequent cases of cyclists using the adjacent sidewalk. But something has to be done to change the context of the street. Underutilized by cars much of the time, it is an inefficient use of urban space, and its capaciousness sends a set of powerful signals to the driver, more powerful than whatever speed limit signs may be present. It represents, to paraphrase Wansink, “mindless speeding.” People drive fast because it feels like they should. They see a wide road, and don’t give themselves much time to see anything else.

And to return to that notion of feedback loops. Wansink noted that with larger portion sizes people became less well adept at judging their calorie consumption; I haven’t seen this study (or maybe I have and have forgotten), but I suspect that the higher speed at which one drives, the less able one is to accurately judge one’s speed. Just a theory.

Sure, we could post yet more signage. We could put increased police patrols along the way. We could run expensive ads showing people what happens to pedestrians when struck by vehicles at 20 mph versus 30 mph. But as Wansink writes, in the context of eating, “it is much easier to change a person’s environment than to change their thinking.”

Posted on Tuesday, April 14th, 2009 at 3:58 pm by: Tom Vanderbilt
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The Three-Feet High Club

From the BBC:

A man faces a hefty fine and a driving ban after being caught having sex with his girlfriend while speeding on a motorway in Norway, police have said.

Posted on Monday, April 13th, 2009 at 9:16 am by: Tom Vanderbilt
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‘What Does It Allow Us to Ignore?’

The philosopher Jacques Ellul once posed “76 Reasonable Questions to Ask About Any Technology,” one of them being: “What does it allow us to ignore?”

In a typically good essay in the WSJ, titled “Machines That Won’t Shut Up,” Christine Rosen raises Ellul’s question in the context of any number of devices that we now talk to, or that talk at us. Some, of course, are driving-related:

When the Canadian technology company IMS recently began selling iLane — a hands-free device that links to your BlackBerry and allows you to use voice commands to open, listen to and respond to your email while driving — it likely fulfilled the wishes of many a time-stressed commuter. According to Discover magazine, the average U.S. city commuter now loses 38 hours every year to delays caused by traffic. ILane offers its users the alluring promise of making safe and efficient use of that time, with the bonus of feeling like Captain Kirk issuing orders from his command chair.

The demonstration video featured on IMS’s Web site shows a stylishly dressed businessman responding to iLane’s overtures about a new email as he cruises along a tree-lined boulevard. “What would you like to do?” murmurs iLane, in its uxorious synthetic female voice. “Check messages,” says our hero, briskly. And he does, with abandon, scheduling appointments, confirming travel arrangements and returning phone calls, his hands never straying from the steering wheel. The company’s marketing materials tout the device as “a true technology breakthrough in personal productivity.”

But there are problems, as Rosen notes:

And there are reasons for concern, too — not least the effect on other aspects of life as those strange artificial voices compete for our attention and require us to enter feedback loops normally reserved for, well, actual human beings.

Their claims to safety notwithstanding, for instance, technologies such as iLane are potentially dangerous distractions for drivers. The research on multitasking is clear: Even when we use hands-free devices for our cellphones, there is something so deeply distracting about carrying on disembodied conversations while driving a car that the National Safety Council has recommended a ban on all talking and texting activities behind the wheel.

What these technologies seem to allow us to “ignore” is the drudgery of the everyday act of driving, as every added bit of multi-tasking leaves us with less cognitive resources for the varying demands of the road.

Rosen’s essay reminded me of some interesting work by Stanford University communications researcher Clifford Nass, who has been studying the dynamics at work in driver-car communication.

One finding:

In tests of volunteers driving automobile simulators in the lab, researchers put their subjects into stressful situations and tested out potential responses from the voice. For example, some drivers received a reproachful warning: “You’re not driving very well and you need to pay more attention.”

“Well, you won’t be shocked to learn that people got angry and actually drove worse,” laughed Nass as he told the story. As the voice ratcheted up its rhetoric (“You really need to be more careful!”), the driving deteriorated further. Finally, when the voice began insisting that the drivers pull over to the side of the road, they responded by getting into accidents.

Nass contends that we can’t help but respond to an in-car computer voice as if it were human; this itself raises all sorts of concerns, like when BMW was having trouble with its 5-Series “voice,” as apparently drivers didn’t like taking directions from a woman (why a person would want yet more chatter in their life is beyond me, but that’s another story).

The gender stereotypes that tripped up BMW also have come through loud and clear in Nass’ experiments, to his dismay. Volunteers are more likely to perceive a male voice as authoritative, even when male and female voices speak exactly the same words.

But if we perceive the car voice as human, which voice should it be?

After deciding that the new voice in the BMW should not be the car itself (as in the TV series Knight Rider), Nass and his colleagues considered other candidates—a golf buddy, a chauffeur, a pilot (dominant and not very friendly) and a person riding “shotgun” (talkative, not very smart)—before settling on a co-pilot, who could take over when the driver was in trouble but who understood that the driver (the pilot) was in charge. The chosen voice was male, somewhat friendly, and competent. He was a hit.

I didn’t see this particular bit studied, but I’d be curious to know about how people’s reaction times vary to a “voiced” warning versus a beep or a whistle, etc. Is there more “processing” that goes on because we do understand it as human?

Posted on Monday, April 13th, 2009 at 7:33 am by: Tom Vanderbilt
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‘Speed Zone Ahead’ and Other Types of Road Ambiguity

I enjoyed this post from Jeff Sommar on the ambiguity inherent in “Speed Zone Ahead” and other road signs. About “Speed Zone,” he writes: “Reading it at face value, which when you think about it, is how street signs should be read, you would think that the sign is alerting you to the fact that you will be able to speed up in the zone ahead.”

He goes on to mention the sign is used to signal increased speed ahead, as well as decreased speed, which I don’t think is actually true (please confirm, any engineers). But his point about the vagueness is well taken. The sign, after all, doesn’t tell you how much the speed is dropping by (or exactly when). As it turns out, the engineers have heard his cry of confusion, and the sign as pictured above is on the way out, according to some chatter on the MUTCD websites (this site shows some of the new configurations, which are yellow rather than white, and state specific decreases — never increases — in speed). As a side note, there’s also some discussion about what the proper placement is of these signs — so drivers have sufficient time to react and slow before hitting a new speed zone and, perhaps, a speed trap.

The “Speed Zone Ahead” sign brings up another issue of mine, which is the problem of having a road marked for, say, 65 mph, which suddenly hits a stretch that is 35 mph — but the road is exactly the same. The “Speed Zone Ahead” sign is thus a rather weak signal in changing behavior. I think compliance would be higher if, for example, the road were made narrower in the slower section; some alternative paving treatments were introduced; another potential solution is “optical speed zones,” the subject of an article in the latest ITE Journal by Steven Latoski — this treatment uses “bars” painted across the road that diminish in proximity as the driver progresses across them, thus increasing the feeling of speed, thus targeting “an instinctive road user reaction of relaxing the accelerator or adjusting the cruise control.”

I also like Jeff’s mention of the “Dangerous Intersection” sign. Given that signalized intersections account for a very high percentage of traffic crashes, perhaps this should be placed at all intersections. I understand the impulse to put up the sign, at least to provide liability coverage; but is that really all that can be done? And does putting the sign up at one location cause one to lower one’s guard at other areas not so marked? Tricky stuff, this traffic engineering.

Anyone else have favorite examples of signs that gave them pause? My favorite is one that says, simply, “No Traffic Signs.”

Posted on Sunday, March 29th, 2009 at 6:41 pm by: Tom Vanderbilt
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Light Reading

I found it surprising that this WSJ story on “red light camera” rage — and I’m waiting for the moment some fool checking his “Trapster” on his PDA blows a light and crashes — made it through an entire article without mentioning a.) the number of people killed in red-light running crashes (uh, more than 9/11 every year); b.) how countries with an increased adoption of the technology have made more impressive gains in their traffic safety records and c.) that rear-end crashes, which critics always cite as rising after installation of the cameras, are relatively minor in nature; while side impact crashes, which studies have shown have been reduced after installation of the cameras, tend to be more serious, and often fatal — to compare them so casually is typical of myopic mainstream-media reporting when it comes to traffic safety. The story notes the study that found that “governments use traffic tickets as a means of generating revenue”; it might also go to the trouble to cite the related study that, while finding truth in that, also found jurisdictions had improved their traffic safety. Traffic fatalities and injuries in and of themselves are a hidden “fine,” or “tax” if you will, that each year cost the U.S. more than the much-touted productively losses due to congestion. Looking also at studies that show tickets reduce the likelihood of a driver subsequently being involved in a fatal crash, fines can also be viewed as expenditure reducers.

Not to mention that the fact that I was taught, as every driver is, to maintain a sufficient following distance from the vehicle ahead — so much so that you could stop in time if the person ahead had to do something like slam on their brakes (particularly at complicated places like intersections).

Posted on Friday, March 27th, 2009 at 2:47 pm by: Tom Vanderbilt
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Situational Awareness

The Daily Mirror reports on the case of a BMW driver whose SatNav nearly sent him off a cliff.

As a bonus they throw in ten memorable “SatNav disasters.”

(Horn honk to Warren)

Posted on Wednesday, March 25th, 2009 at 6:00 pm by: Tom Vanderbilt
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What’s the Effect of Rubbernecking on Traffic Flow?

We all intuitively know that a crash — or even a disabled vehicle or a piece of interesting debris on the roadside — can disrupt the flow of traffic. Cambridge Systematics has suggested that as much as 25% of congestion in the U.S. is due to “incidents.” Some of this due to physical loss of highway capacity (e.g., a blocked lane). But how much is actually due to drivers slowing down to rubberneck? (the dreaded “gaper’s block,” as they say in the Midwest)

Previous estimates have been based largely on models or “macroscopic” calculations. But an interesting bit of research — one version is here — by a Dutch team (Victor Knoop, Serge Hoogendoorn, and Henk J. van Zuylen, at the Delft University of Technology), to be published as part of this conference, has examined the “microscopic behavior” of drivers at crash sites, as well as quantified the actual loss in traffic capacity due to rubbernecking.

How did they do it? The authors write: “The observation team waited at the Traffic Management Center in the centre of the Netherlands until an accident had occurred somewhere nearby, after which it flew with the helicopter to the accident location. From the moment of arrival, traffic operations for both directions were recorded. From the other side of the road, the incident was visible but there was no physical obstruction.” They point out, by the way, that the helicopter was high enough to itself not be a cause of traffic disruption.

As pictured above, a light truck overturned near the city of Apeldoorn. One lane (in the ‘bottom section’ in the photo above) was closed for the sake of emergency response. Not surprisingly, given that a lane was missing, and two lanes had to merge, the researchers a large drop in “outflow capacity” in the section closest to the overturned van.

But what is striking is the airborne researchers observed a sizable effect — roughly a 50% capacity reduction — in the opposite bit of highway, in which no lanes were blocked. The video of this is rather amazing: At roughly the position that affords the best view of the crash, the traffic begins to bunch, as it does in stop-and-go congestion, even though the road ahead is otherwise clear. One vehicle, the “leader” is essentially slowing to look at the incident, creating in essence a backward “shock wave” that everyone else drives into. Once in the slowing wave, their curiosity is no doubt aroused and so they too continue to creep along for a look. At the exact point of the wreck, the traffic again begins to accelerate.

This raises the idea of the magical “first driver” in a traffic jam you may have wondered about as a child — the idea that there must be some driver at the head of even the longest traffic jam, and if only they would get going, or hadn’t slowed to begin with, things wouldn’t be so bad for us, etc. It also raises Thomas Schelling’s description of rubbernecking in the classic book Micromotives and Macrobehavior: Because they’ve already been made to wait because of everyone else’s look, each individual driver feels they too have the right to look themselves. Each person’s five seconds adds up to incremental delays (“it is a bad bargain,” he wrote). If everyone could only agree not to look, the congestion actually would not form.

There were a number of other interesting observations made. On the section of highway without any physical obstruction, the speed of vehicles in the left lane drops faster than those in the right (the authors speculate that left-lane cars are probably going faster to begin with; that they may be closer to the event and thus more distracted; and that there are more slower-moving trucks in the right lane).

Another curious phenomenon is that as the lead vehicle accelerates past the point of the crash, the time that the following driver begins to also accelerate varies more widely than under the “normal” conditions of heavy congestion. It is as if some drivers are simply more distracted by the sight of the crash, or perhaps some drivers instinctively behave with more caution in the immediate aftermath (the presence of emergency personnel may also affect driver behavior). All drivers react more slowly than in typical conditions, but some react much more slowly.

In any case, this is fascinating research that suggests the traffic impacts of rubbenecking are greater than those found in previous work.

Posted on Tuesday, March 10th, 2009 at 4:18 pm by: Tom Vanderbilt
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Every Driver’s Nightmare

Don’t know the whys or whos of this video (and has this driver been canned yet?) But it goes without saying that Romania is among the least safest places to drive in the European Union.

[UPDATE: See comments for further developments…]

Posted on Monday, March 9th, 2009 at 2:08 pm by: Tom Vanderbilt
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I Guess This Means the Baby Wasn’t In a Rear-Facing Car Seat?

As if drivers on cell-phones weren’t a big enough problem already, this one takes it to a new level. Via Jezebel:

Genine Compton of Dayton, Ohio, was pulled over on Thursday morning after police spotted her breastfeeding her baby (and talking on her cell phone!) while driving her other children to school. “If my child’s hungry, I’m going to feed it,” Compton, who is facing 180 days for child endangerment, says.

Jezebel notes: “Genine! If your baby needs to eat, that’s fine. But it’s probably best for both of you if you stop the car and get off the phone first, no?”

Yeah, and it’s, uh, also better for everyone else outside of her car.

Posted on Monday, March 2nd, 2009 at 10:48 am by: Tom Vanderbilt
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The Daily ‘Hang Up and Drive’ Dispatch

Gary Richards solicits driving-on-cellphone horror stories.

The worst incident I came upon was about five years ago as a newspaper reporter in Anderson, when a young women was on a cell phone when she pulled out in front of a large truck. She was at a stop sign and stopped. But, for some unknown reason, she pulled out into the traffic, which was traveling around 55 mph. The truck had no time to stop and crashed into her. The girl died instantly. It was a very sad incident.

Posted on Monday, March 2nd, 2009 at 9:08 am by: Tom Vanderbilt
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The Dubious Disctinction Between “Good” and “Bad” Drivers on Cell-Phones

I was bothered by this assertion in an editorial on cell-phones in cars:

Motorists who drive carelessly while on the phone — we’ve all seen them — are a hazard and should be penalized. The same is true for those who drive carelessly while operating their CD players, adjusting their GPS devices or fussing with their kids.

But a motorist driving attentively at a lawful speed on a safe, straight stretch of Interstate 5 should not be pulled over because of a telephone conversation.

Yes, obviously people driving recklessly, whether distracted or not, should be pulled over. But to assert that a motorist “driving attentively” on a “safe, straight stretch” of road while talking on a phone is beyond concern is a gross oversimplification of the emerging science.

It reminds me of a night, many years ago, when I was much younger and much more car-dependent (two conditions I do not long to return to), when I drove home in what can only be called a state of substantial intoxication — something I only became dimly aware of a number of minutes into the trip. Somewhat panicked, I rigorously drove the speed limit, and locked my attention on the road — “a safe, straight stretch” (I’ve said it before, “safe” is a relative term; the only objectively safe road is the one that’s never traveled).

In any case, by any external measure, I was just another law-abiding, prudent motorist. The fact was, however, that my physical impairments began with the first drink of the night and only got progressively worse, and that I very likely may have not been able to stop in the face of an unexpected “path intrusion,” or not seen a pedestrian in the crosswalk in time to react, etc. But I would not have been readily aware of the scale of this performance decrement, as all my attention was on keeping between the lanes and going the speed limit — which is not necessarily the same thing as safe, attentive driving. Of course, I may indeed have been drifting across lanes; but this feedback is not something always immediately apparent to drunk drivers.

This is the condition that cell-phone conversation presents. Even if there is not obvious “fiddling” with the phone (at least the person is aware of their distraction in that case) or drifting across lanes, there is still some portion of mental workload — higher than one would devote to a billboard, a passenger, or the radio — being dedicated to the task. The driver may still have enough left to operate the car in a seemingly effective manner, but it still leaves open the very good possibility that their performance would be impaired if something out of the ordinary were to happen. To our minds, we may be driving fine, by a certain measure, but just as we are fully unable to measure our own extent of distraction (often, one only realizes this afterward, as the miles traveled while talking have suddenly vanished from recollection, a sign of cognitive shedding), we also cannot predict how that distraction would leave us equipped to react to something unexpected. A car traveling the speed limit and staying within lanes is safe until the driver rear-ends someone who has unexpectedly come to a stop on the highway.

I am reminded of another good excerpt from a paper I referenced earlier this week, by Peter Hancock and colleagues, “On the philosophical foundations of driving distraction and the distracted driver,” in a recent book titled Driver Distraction: Theory, Effects, and Mitigation:

Driving, as we have seen, is a satisficing task. It is one in which all drivers frequently, and on certain occasions necessarily, fail to maintain their attention toward the “correct” source of attraction. Infrequently and unpredictably, these momentary failures encounter the precise environmental circumstances that induce collision. In Haddon’s terms, we “meet the tiger.” Society is content, in general, to chastise those unlucky drivers who find themselves involved in these rare collisions. This does not, of course, exempt those drivers who consciously make the decision to neglect to neglect their responsibilities. However, if collisions became more frequent by several orders of magnitude, society would not single out these ‘bad’ individuals but would seek to make corrections at a systemic level. However, we have been generally content to ratify our collective, institutional schizophrenia, which ‘blames’ the ‘bad’ drivers while encouraging the production of ever greater numbers of technologies that inevitably redirect drivers’ attention from the ever more satisficed task of vehicle control.

The editorial I referred to in the opening sentences wants to make this easy distinction between the “good” and “bad” driver. But it is not so clear; there are many “good” intoxicated drivers who become “bad” only when their blood is analyzed at a crash scene. There is also the problem of ethics: The individual driver may think talking on the phone is a good idea because they’ve done it “all the time” and they do it safely. But what is the moral consequence of participating in a behavior with known negative consequences for driving performance to other people? Already, just by getting behind the wheel, we are doing one of the few things in our life by which we easily have the capability to take someone’s life, accidentally or not; what is the ethical dimension to raising that likelihood, even marginally?

There is always the rejoinder, but why haven’t we seen a big increase in crashes and fatalities with phone use? The first point is there have been any number of fatalities already attributed to cell-phones; the second point is that most people do not talk most of the time, leaving more aware drivers to account for others’ mistakes — as a generation raised on Twitter hits the road it’s anyone’s guess. Another issue is that, perhaps through sheer luck, a majority of drunks make it home every night (should we thus do away with DUI?) And cars of course keep getting safer, which is no consolation to anyone outside the car, a condition common to most of us, even in America. In any case, this line of inquiry misstates the problem. The real question is not why there hasn’t been an increase but why we haven’t seen a great decline in this country (the recent small decline one was mostly due to economic factors) of traffic fatalities? Yes, driving per mile has become ever safer, but per-head of population the number killed is stubbornly similar to decades past. With each increase in car and road safety we seem to find new ways to make our own performance a touch more dangerous.

Posted on Friday, February 27th, 2009 at 10:19 am by: Tom Vanderbilt
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Fooled Drivers, or Foolish Drivers?

I’m not sure if, lurking somewhere in NHTSA’s databases, there’s a category for “Car-House Crash” (no worries about coding for culpability there!), but, judging by the news reports I get, it happens more than you’d think.

It recently happened to a man in Toronto. Twice. Within three weeks. The article in the Toronto Star notes that residents and engineers think poor road design is to blame:

Johansen and other area residents blame the accidents on a reconfiguration of the Park Lawn-South Kingslea intersection a few years ago. The new intersection was moved a few metres west, and curves to the left just before the stop sign. But a laneway to the right, near the stop sign, can create an optical illusion that may fool some drivers into thinking it’s South Kingslea, and that the stop sign is in a traffic island in the middle of the intersection. As a result, they end up on the wrong side of the sign.

At least that’s the theory of Allan Smithies, who’s in charge of traffic planning in that area.

I haven’t been to the intersection in question, and it’s hard to draw inference from a photo, but as pictured above, I’m not quite sure what the source of confusion is. I see a Stop Sign, I quite plainly see a house. More importantly, I see other houses. It is a neighborhood. Neighborhoods are places where you don’t drive at speeds that would prevent you from not being able to crash into a house.

The local response was to place a set of “jersey barriers” in front of the house. The idea of living like the American embassy in Beruit didn’t please the homeowner.

But after assessing the path of the two vehicles that ended up in his house, Johansen said the barricade would be more likely to stop another vehicle if it was put up on the other side of South Kingslea, next to the stop sign and across the sidewalk on the east side of Park Lawn.

“I don’t want that ugly cement wall across my front yard, especially when it won’t stop another car,” unless it’s positioned across the laneway, he explained.

Rather than allow the barrier to be dropped in his yard, which he says would stigmatize his home as the target for airborne vehicles and not prevent further assaults, Johansen said he told city workers to stick it.

I can utterly side with the homeowner’s sentiment on this. Residential streets are not meant to be places for guard-rails, concrete barriers, and other aspects of the “forgiving road,” just as residents should not have to wear crash helmets when they go out for a walk. As I’ve argued here before, I’d rather see trees planted mid-block, every block, in the center of the block. Apart from that, there must be some better solution here than jersey barriers, any host of traffic calming treatments.

Of course, one doesn’t usually have to dig too deep in these stories to find the real source of the problem.

Around 1 a.m. yesterday, a car driven by a 25-year-old man hit a curb, flew through the master bedroom window of the house and landed on the residents’ bed. Police say alcohol was a factor in the crash and the driver has been charged with impaired driving.

This takes “breaking and entering” to a new level. But in any case, we see that it wasn’t necessarily some strange road illusion causing the problem, it was the fact that the driver was hammered. He was creating his own illusions.

What’s more, the article notes:

Neighbours in the area say many people don’t heed the nearby stop sign, which has been taken out a few times by previous collisions.

Now, I agree that good design of any sort should help users avoid unnecessary mistakes, or at least not make them more prone to make mistakes (TV remote-controls are notorious for this). But at what point do we say enough’s enough? As Hans Monderman has said, there are some drivers which no road can save. As, I’ve argued in Traffic, bringing the “foolproof” design of the forgiving road into places like neighborhoods not only cheapens the neighborhood, it increases the risk-taking behavior of drivers. I noticed that one poster referred to the fact that the “sightlines” were good; the problem with “sight distance” is that drivers simply consume the extra visibility with greater speed. It could even be that the stop sign itself is a problem — drivers are looking at that rather than scanning the actual terrain. Or maybe it’s just a Canadian snow and ice thing.

Now, I realize I’m sounding off here, and I recognize that traffic engineers, who must wrestle with the many-footed beast of human behavior, do not have an easy job by any means. If this finds its way to Mr. Smithies (or the homeowners) I’d be curious to hear more about the case.

(Horn honk to David)

Posted on Thursday, February 26th, 2009 at 10:45 am by: Tom Vanderbilt
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Merge Overkill

The Oregonian’s Joseph Rose is wished dead by an irate reader after discussing the potential benefits of “late merging.”

This made me all nostalgic as it was this kind of vitriol that launched me on the Traffic road: How could this simple activity stir such passion? While I am delighted to see the issue receiving further elaboration and exploration, I should only clarify here that I was not advocating a Universal Late Merge plan. There are circumstances where this behavior would actually make things worse. But the point was more that in certain scenarios, it would work better (better traffic flow, shorter queues, etc.), and that of course it would be better if drivers were instructed what to do — so as to not set off anger against the minority late merger position by early merge vigilantes — and then, having been instructed as how to properly merge, people then actually left these old prejudices behind (which trials have shown does not always happen).

But this is admittedly complex, for what makes late merging a better overall system for some highway segment may depend on a change to a certain level of congestion (in which case you’d need real-time ‘dynamic’ signage announcing the late merge), or it may depend on the number of lanes on the highway, or it may depend on the volume of trucks on a particular ‘facility.’ The correct cure depends on the set of symptoms.

Posted on Tuesday, February 24th, 2009 at 3:53 pm by: Tom Vanderbilt
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What’s the Real Risk of Older Drivers?

Nothing brought the issue of older drivers into sharper focus than the 2003 crash at the Santa Monica Farmer’s Market, in which a 86-year-old man who had confused accelerator for brake killed nine people and injured scores more. As often happens in the media, something that had once basked outside of the light of attention suddenly became an “epidemic,” and untold numbers of stories warned us of the specter of the aging Baby Boom behind the wheel. This is, undoubtedly, a real issue, and the problems of the older driver do merit societal attention, but it is also likely that the circumstances of the Santa Monica event may have helped skew the actual risk posed: It was novel, it represented something out of our control, and, compared to most traffic fatalities at least, a large number of people were involved.

A new paper by Bryan Tefft, a researcher at the AAA Safety Foundation, published in the latest edition of the Journal for Safety Research, tries to put the older driver risk question into context, addressing some shortcomings of previous studies, most of which have not, as he notes, “analyzed responsibility for — as opposed to mere involvement in—crashes that kill other road users in relation to driver age, and none has done so while taking the amount of driving done by drivers of different ages into account.”

It is a truism of road safety research that a kind of u-shaped curve exists, in which the riskiest drivers are found at both ends of the age spectrum, as shown in the chart below, which comes from a Rand study (more on that later).

But this leaves out various, but important, parts of the risk equation, including: Which drivers (if any) bore a greater responsibility for the crash (an admittedly “noisy” bit of data), and the risk posed by certain classes of drivers to other drivers.

In any case, Tefft, using data from the FARS database, as well as “exposure” data from the National Household Travel Survey (and he notes using two different sources is a limitation of the work), comes to some interesting conclusions.

As other studies have found, he notes older drivers do have a greater risk of being involved in a fatal crash, but that this fatality risk is largely to themselves, as they are more likely, owing to increased “fragility,” to die in a crash than a younger driver. But as Tefft notes, “the degree to which older drivers’ risk to other road users is elevated depends strongly upon whether risk is measured on a per-driver, per trip, or per-mile basis.”

As an example, he writes, “if a randomly-selected driver in his or her thirties and a randomly selected driver aged 85 or older were to drive equal numbers of miles, the older driver would be over 1500% more likely than the younger driver to be responsible for and die as a result of a crash, and about 220% more likely than the younger driver to be responsible for a crash fatal to an occupant of another vehicle or a non-motorist.”

But, of course, most older drivers don’t drive as much as younger drivers, and they drive differently (i.e., they modulate risk based on their ability by choosing only certain roads, or certain times of day to drive, they may drive more slowly — insert Florida joke here — etc.). And so, while “a randomly-selected driver aged 85 or older is about 720% more likely than a randomly selected driver aged 30 to 39 to die in a crash, but only about 0.8% more likely to be responsible for a crash fatal to an occupant of another vehicle or a non-motorist, over the course of a year.” Per trip, the risk older drivers pose to others is “not statistically different” from drivers 30 to 39.

For the greatest source of risk from “without,” then, we need to look at the other end of the age spectrum. Tefft writes: “Drivers under age of 20 are responsible for more than twice as many deaths of occupants of other vehicles and non-motorists as are all drivers aged 70 and older.”

Tefft’s findings are supported by another paper — which uses another methodology (based on a technique created by Steven Levitt and J. Porter in this paper, which uses the drivers involved in fatal crashes as a surrogate for exposure) — namely, the Rand study mentioned above, “Regulating Older Drivers: Are New Policies Needed?,” by David S. Loughran, Seth A. Seabury, Laura Zakaras. They conclude: “In summary, we find that older drivers are only slightly likelier than other drivers to cause an accident but are considerably likelier to be killed in one. Younger drivers, on the other hand, are considerably likelier than other drivers to cause a crash, drive much more frequently than older drivers, and are less susceptible to fatal injuries than older drivers are.”

There are good reasons to be concerned about older drivers, but the news stories suggesting the greatest threat to our safety might come at the wrinkled hands of aging drivers seems somewhat misplaced. In strict terms of cost and benefit, it would seem wiser (assuming older drivers continue to do less driving than their younger peers), rather than rolling out new “mandatory retesting” programs in state DMVs (granted, one must leave open the possibilities these already existing programs have impacted the older driver crash rate), to ratchet up GDL programs at the other end — it really is shocking that driver’s licenses, in states like North Dakota, can still be had at age 14. Or simply cracking down on the most risky drivers, regardless of age, rather than blithely allowing people with clear patterns of dangerous driving to inhabit the roads (and, by the way, please don’t start on the sob story, ‘but it’s the U.S., you can’t function without a car…’). Demonizing older drivers may also subtly suggest to younger drivers, in their 30s say, that they have much less to worry about, when as Teftt’s per trip numbers indicate, may not be the case.

Posted on Friday, February 20th, 2009 at 12:31 pm by: Tom Vanderbilt
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And You Thought Driving Tests Were Stressful for the Students

The BBC reports that a driving instructor is suing for damages over a driving test.

Mr Carmichael said he recorded 14 faults with the driving of the woman taking the exam, claiming five were serious and one dangerous.

He’s suing the insurer of the exam car, not the would-be student (who, uh, failed).

Ms Tait asked Mr Carmichael, a former driving instructor, if he was seriously telling the court that this incident, if it occurred as he said, was the worst he had experienced in over 12 years of having learner drivers at the wheel.

He said: “Yes it was.”

Posted on Wednesday, February 18th, 2009 at 9:32 am by: Tom Vanderbilt
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Jack Martin on Hypermiling

Interesting road-trip with 2008 hyper-miling champion Jack Martin, particularly for his comments about trucks and bikes.

(Thanks Ed!)

Posted on Monday, February 16th, 2009 at 3:36 pm by: Tom Vanderbilt
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Human Factors

Just for dark humor — it’s Friday, after all (and appropriately, it’s Friday the 13th).

(Horn honk to Roadguy)

Posted on Friday, February 13th, 2009 at 9:35 am by: Tom Vanderbilt
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Traffic Tom Vanderbilt

How We Drive is the companion blog to Tom Vanderbilt’s New York Times bestselling book, Traffic: Why We Drive the Way We Do (and What It Says About Us), published by Alfred A. Knopf in the U.S. and Canada, Penguin in the U.K, and in languages other than English by a number of other fine publishers worldwide.

Please send tips, news, research papers, links, photos (bad road signs, outrageous bumper stickers, spectacularly awful acts of driving or parking or anything traffic-related), or ideas for my Transport column to me at:

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Upcoming Talks

April 9, 2008.
California Office of Traffic Safety Summit
San Francisco, CA.

May 19, 2009
University of Minnesota Center for Transportation Studies
Bloomington, MN

June 23, 2009
Driving Assessment 2009
Big Sky, Montana

June 26, 2009
PRI World Congress
Rotterdam, The Netherlands

June 27, 2009
Day of Architecture
Utrecht, The Netherlands

July 13, 2009
Association of Transportation Safety Information Professionals (ATSIP)
Phoenix, AZ.

August 12-14
Texas Department of Transportation “Save a Life Summit”
San Antonio, Texas

September 2, 2009
Governors Highway Safety Association Annual Meeting
Savannah, Georgia

September 11, 2009
Oregon Transportation Summit
Portland, Oregon

October 8
Honda R&D Americas
Raymond, Ohio

October 10-11
INFORMS Roundtable
San Diego, CA

October 21, 2009
California State University-San Bernardino, Leonard Transportation Center
San Bernardino, CA

November 5
Southern New England Planning Association Planning Conference
Uncasville, Connecticut

January 6
Texas Transportation Forum
Austin, TX

January 19
Yale University
(with Donald Shoup; details to come)

Monday, February 22
Yale University School of Architecture
Eero Saarinen Lecture

Friday, March 19
University of Delaware
Delaware Center for Transportation

April 5-7
University of Utah
Salt Lake City
McMurrin Lectureship

April 19
International Bridge, Tunnel and Turnpike Association (Organization Management Workshop)
Austin, Texas

Monday, April 26
Edmonton Traffic Safety Conference
Edmonton, Canada

Monday, June 7
Canadian Association of Road Safety Professionals
Niagara Falls, Ontario

Wednesday, July 6
Fondo de Prevención Vial
Bogotá, Colombia

Tuesday, August 31
Royal Automobile Club
Perth, Australia

Wednesday, September 1
Australasian Road Safety Conference
Canberra, Australia

Wednesday, September 22

Wisconsin Department of Transportation’s
Traffic Incident Management Enhancement Program
Statewide Conference
Wisconsin Dells, WI

Wednesday, October 20
Rutgers University
Center for Advanced Infrastructure and Transportation
Piscataway, NJ

Tuesday, March 8, 2011
Ontario Injury Prevention Resource Centre
Injury Prevention Forum

Monday, May 2
Idaho Public Driver Education Conference
Boise, Idaho

Tuesday, June 2, 2011
California Association of Cities
Costa Mesa, California

Sunday, August 21, 2011
American Association of Motor Vehicle Administrators
Milwaukee, Wisconsin

Wednesday, October 26, 2011
Attitudes: Iniciativa Social de Audi
Madrid, Spain

April 16, 2012
Institute for Sensible Transport Seminar
Gardens Theatre, QUT
Brisbane, Australia

April 17, 2012
Institute for Sensible Transport Seminar
Centennial Plaza, Sydney
Sydney, Australia

April 19, 2012
Institute for Sensible Transport Seminar
Melbourne Town Hall
Melbourne, Australia

January 30, 2013
University of Minnesota City Engineers Association Meeting
Minneapolis, MN

January 31, 2013
Metropolis and Mobile Life
School of Architecture, University of Toronto

February 22, 2013
ISL Engineering
Edmonton, Canada

March 1, 2013
Australian Road Summit
Melbourne, Australia

May 8, 2013
New York State Association of
Transportation Engineers
Rochester, NY

August 18, 2013 “Ingenuity” Conference
San Francisco, CA

September 26, 2013
TransComm 2013
(Meeting of American Association
of State Highway and Transportation
Officials’ Subcommittee on Transportation
Grand Rapids MI



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