Archive for the ‘Traffic Psychology’ Category

Children at Play (And at the Wheel)

My latest Slate column is up, examining the problems with “Children at Play” traffic signs (the headline, which is never the writer’s, may overstate things a bit…)

If the sign is so disliked by the profession charged with maintaining order and safety on our streets, why do we seem to see so many of them? In a word: Parents. Talk to a town engineer, and you’ll often get the sense it’s easier to put up a sign than to explain to local residents why the sign shouldn’t be put up. (This official notes that “Children at Play” signs are the second-most-common question he’s asked at town meetings.) Residents have also been known to put up their own signs, perhaps using the DIY instructions provided by eHow (which notes, in a baseless assertion typical of the whole discussion, that “Notifying these drivers there are children at play may reduce your child’s risk”). States and municipalities are also free to sanction their own signs (hence the rise of “autistic child” traffic signs).

Posted on Wednesday, May 18th, 2011 at 9:09 am by: Tom Vanderbilt
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Why Traffic Slows at Tunnel Approaches

Via ENR, an interesting piece on tunnels, shockwaves, and traffic psychology.

“If everybody goes the same speed and distance and nobody uses the brakes, you can through-put more vehicles,” Khattak said.

These tunnel-driving behaviors are so notorious that the proposal for the group interested in widening the HRBT suggests making the tunnel four lanes in each direction and the approaches only three lanes.

Scerbo noted, though, that regardless of how many lanes are added at the tunnels, many drivers will still brake.

Although some of these driver reactions can’t be controlled, the physical environment they’re reacting to can.

“We’ve tried to counter this whole perception that you’re driving into a hole in the water… so you don’t feel like you’re going into a different environment than you’re coming from,” said Dwayne Cook, regional operations manager for the Virginia Department of Transportation.

Posted on Wednesday, November 10th, 2010 at 11:40 am by: Tom Vanderbilt
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Asymmetric Information on I-95

In a footnote to Traffic, MIT’s Moshe Ben-Akiva discusses the varying strategies of dynamic tolling:

“You may want to charge people for time they actually save. That will mean if congestion builds up on the tolled road you reduce the price. On the other hand, you want to maintain a certain level of speed on the toll-road. If congestion builds up you want to increase the toll so as to not have stop-and-go traffic on the tolled road. There is some confusion going on right now as to what strategy is best.”

it seems that confusion is still out there, based on this dispatch from the Miami Herald.

Traffic engineers assumed high tolls would deter drivers from using express lanes. Wrong.

Many drivers, like Perkovich, assume high tolls mean the toll-free lanes are clogged. Could be true, but the tolls rise mainly due to the number of drivers willing to pay a toll.

Perhaps it’s not easy to make these decisions at high speed in a split second. Perhaps there’s some weird signaling effect going on in which higher prices lead to higher demand (for reasons of perceived quality or some other factor). Maybe the tolls aren’t high enough to deter drivers. Maybe the problem would vanish if drivers were given a more precise sense of time savings (as far as I know they are not). But South Florida drivers are not the first to be undeterred by higher tolls.

Before HOT lanes were launched on an I-10 commuter highway serving the Houston area, the Texas Transportation Institute based at Texas A & M University made an extensive study of driver attitudes and beliefs.

As many as 20 percent of the participants in several focus groups incorrectly interpreted the HOT lane toll as an index of traffic congestion in the free lanes, said Susan Chrysler, an institute research psychologist.

“Even after I showed them a video that explained it, they still misunderstood it,” Chrysler said. In Florida, DOT has responded with a crash public information campaign. A prominent message on the Express Lane website,, clearly explains the system. And SunPass holders recently received a special mailing with the same message: higher tolls may mean a slower ride.

The market is still working, though perhaps not as rationally as might be hoped.

Despite the misunderstanding, the Express Lanes are easing traffic. Santana says the toll lanes are maintaining a comfortable 16 mile-an-hour speed advantage over the free lanes. A typical $2.50 to $3.00 rush hour toll usually buys a 45-mph drive between South Broward and downtown Miami, according to DOT data.

Posted on Friday, April 2nd, 2010 at 2:22 pm by: Tom Vanderbilt
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The Bird, the Wave, and the Shaka

My latest Slate column is up, and the subject is the informal language of the road (and yes I know about the Australian ‘waggling pinkie,’ but for editing reasons, etc., it got cut). For space reasons I also didn’t get into the whole gamut of bicyclist/motorcyclist/pedestrian gestures — though I remember at one Brooklyn crosswalk I was turning right and a person about to enter the crosswalk did an elaborate bow/sweep of the hand to urge me through, to which my reply was to try to apologize for violating the right of way. Then there was a secondary round of strange gestures in response to the first. And then, of course, the driver behind me honked.

Posted on Tuesday, February 9th, 2010 at 1:34 pm by: Tom Vanderbilt
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‘My God, It’s Full of Stars!”

I can’t help but view the image above and think of 2001, with some impenetrable black slab tilted horizontally and laid upon the city. The sign, which comes from Toronto, has been the source of some puzzlement over its origin or purpose — maybe someone in actual authority can provide the final answer as to what this signage means and why it needs to be in place (although, I will admit, the sign gains in strange, mythic stature the less one knows about it). It seems to have something to do with plowing — and monolithic refers to its construction — but are sidewalks plowed by trucks? (and if it’s plowed in the way the above image suggests, wouldn’t that dump a bunch of snow on that very sidewalk?) Why only a monolithic sidewalk there, and not anywhere else? What’s a non-monolithic sidewalk called?

And as reader Bruce notes, the sign has even prompted a searching inquiry into self-effacing signage and Canadian national identity.

Posted on Friday, January 29th, 2010 at 11:23 am by: Tom Vanderbilt
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The Laboratory on Wheels

My latest Slate column is up — a survey of the various psychology experiments that have been conducted on subway systems (particularly NYC’s) throughout the years.

Here’s a fragment:

Although subway studies had their heyday in the ’70s, they’re as old as public transit itself. The seminal urban sociologist Georg Simmel, in a famous passage from his 1912 volume Melanges de Philosophie Relativiste, was struck by the new spatial and sensorial regimen that transit provided. “Before the appearance of omnibuses, railroads, and street cars in the nineteenth century, men were not in a situation where for periods of minutes or hours they could or must look at each other without talking to one another.”

By 1971, Erving Goffman, in his book Relations in Public, was noting that a ritual of what he called “civil inattention” had taken hold on the subway as in other spheres of city life: We acknowledge another person’s presence, but not enough to make them “a target of special curiosity or design.” Or, as the authors of the essay “Subway Behavior,” (in the book People and Places: Sociology of the Familiar) put it, “subway behavior is regulated by certain societal rules and regulations that serve to protect personal rights and to sustain proper social distance between unacquainted people who are temporarily placed together in unfocused and focused interaction.”

What much subway psychology seeks to understand, however, is what holds these rules in place, and what happens when they are violated. In one of the most well-known studies, social psychologist Stanley Milgram had students spontaneously ask subway riders to give up their seats. As Thomas Blass recounts in The Man Who Shocked the World, this experiment arose from the seeming erosion of a subway norm. As Milgram’s mother-in-law had posed it to him: “Why don’t young people get up anymore in a bus or a subway train to give their seat to a gray-haired elderly woman?”

Posted on Tuesday, November 17th, 2009 at 9:11 am by: Tom Vanderbilt
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Do Men and Women Commit Different Types of Driving Violations?

This was a question posed to me by an audience member at a recent speaking engagement, based on his observation at his small town’s local courthouse that males seemed to predominate on the speeding offenses, while women seemed more prone to things like traffic signal/stop sign violations.

It’s an interesting question, one that, like many things in traffic, I imagine is difficult to tease out of the official citation statistics (as that wouldn’t give us the exposure data, among other things).

It did put me in mind of a recent study, “Committing driving violations: An observational study comparing city, town and village,” by Tova Rosenbloom and colleagues at Israel’s Bar Ilan University, published in the most recent Journal of Safety Science. This paper looked at five traffic violations (“(a) not wearing a seat belt (seat belt violation); (b) not using a safety seat for a child (safety seat violation for children); (c) not using a speaker while speaking on the phone (on-phone violation); (d) failing to comply with a ‘give way’ sign (‘give way’ sign violation); and (e) stopping in an undesignated area (undesignated stop violation).”) in three settings: City, town, small village.

There was a clear gender effect, but essentially it was that men were more likely to commit violations of any type than women (I didn’t see it gender data coded by violation type), which is not surprising.

But there was another, perhaps more interesting finding: The highest level of violations came not in a city like Tel Aviv, but in the villages (which had around 3,000 and 800 residents).

The researchers speculated a number of reasons: The more complex city driving environment challenges drivers and forces them to pay more attention (they also feel it to be riskier, even if it actually isn’t, which explains greater seat-belt compliance) there may be less law enforcement in the smaller areas, the drivers in the small towns may be more likely to be local drivers (whose familiarity with the road environment breeds a relaxed attitude toward whatever signals and regulations are in force).

And if anyone has seen any studies examining violation types by gender, please advise.

Posted on Wednesday, November 4th, 2009 at 9:00 am by: Tom Vanderbilt
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The Taking of Pelham’s Trees

Apparently this issue has been around awhile. From a letter to the New York Times, 1999:

To the Editor:

Re ”Drivers Fear Leafy Menace by the Side of the Road” (Sept. 19): Pelham Parkway is not a limited-access highway; it is a parkway, a road that connects Pelham Bay Park with Bronx Park. Coincidentally, it now connects the Bronx River Parkway with the Hutchinson River Parkway and the New England Thruway (I-95). It was designed for light pleasure traffic at speeds of 25 to 30 miles per hour, not 50 to 60 m.p.h.

When people fall asleep at the wheel, are cut off by another vehicle or seek to avoid an animal in the road and hit one of the trees transplanted from the subway construction on the Grand Concourse, it is not the fault of the tree, nor the design of the road. I would hate to see the trees removed simply because motorists are not observing the speed limit.

If the police would enforce the speed limit on Pelham Parkway, the city would make money on the road instead of spending it. If the road could have been redesigned, you could be sure the master builder (and destroyer) Robert Moses would have rebuilt it after his failure to complete the Sheridan Expressway, which would have been the main east-west roadway to compliment the Cross Bronx Expressway.


Morris Park, Bronx

Posted on Wednesday, August 26th, 2009 at 8:36 am by: Tom Vanderbilt
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How Aware Are We of Our Own Distraction?

One factor that promotes overconfidence in one’s ability to “safely” multitask while driving is the idea that we cannot often correctly monitor our own level of vigilance.

To wit, a study reported in the New Scientist notes:

A CAR’S judgement on the driver’s levels of alertness could be more reliable than the driver’s own perception of it.

So say Eike Schmidt of car manufacturer Daimler in Böblingen, Germany, and his team, after tests on volunteers during a 4-hour drive along the autobahn. To make the drive as boring as possible, the drivers were asked not to chat or listen to the radio.

Every 20 minutes, the team asked the volunteers how attentive they were feeling. They also tested the volunteers’ reaction times by asking them to push a button attached to their thumbs every time they heard a certain tone. Each driver’s heart rate and brainwave frequency, which are indicators of attentiveness, were also recorded during these tasks.

The team found that while all measures of alertness declined over the 4-hour period, in the final hour the drivers reported feeling more vigilant than the physiological tests suggested.

This relates to a point I tried to raise in Traffic — that drivers are not only distracted, but unaware of their level of distraction.

William Horrey and colleagues found a similar result in a study that looked at drivers on mobile devices on a closed track. As other studies have found, their were “performance decrements” while using a hand-held and hands-free device versus “baseline driving,” but what was interesting here is that subjects’ estimates of how distracted they were had little to do with the actual level of distraction:

[I]n some cases, the subjective measure of distraction was in the opposite direction of the actual distraction effect. That is, drivers that estimated the smallest (or no) distraction effects exhibited the largest ones. In general, a disconnect between performance and awareness was consistent across driving measure and phone type.

Interestingly, in this study, the researchers suggested it was not overconfidence per se, but a “failure of perception,” underpinning the disconnect. Just as a fatigued driver does not quite know the point at which his fatigue will become deadly, nor does the distracted driver know the exact tipping point moment where they will miss something they might have otherwise detected.

Posted on Monday, August 17th, 2009 at 3:20 pm by: Tom Vanderbilt
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Did You See How Fast That Car Was Going? (It Depends on the Model)

I’m fascinated by the ways our mental models can influence how we interpret and behave in the world of traffic. A new study by Graham Davies, “Estimating the speed of vehicles: the influence of stereotypes,” in Psychology, Crime and the Law, looks at this is an interesting way.

As described by BPS, Davies “played ten-second video clips of a BMW and a (smaller, less powerful) Volkswagen Polo to 42 undergrads and asked them to estimate how fast the cars were going. Based on past research showing that participants expect BMWs to be driven faster than Volkswagen Polos, Davies thought that the students would overestimate the speed of the BMW. In fact, he found the opposite. Participants tended to overestimate the speed of the Polo, perhaps because it was a noisier car, and smaller vehicles are generally perceived as going faster than larger cars.”

There was a bias here, but it seemed to be a perceptual bias.

“A second experiment pulled out all the stops in an attempt to provoke participants to rely on their driver stereotypes. Participants were told that the BMW was driven by a young male, and the Polo by a 62-year-old; they were shown photos of the drivers; and they were asked to speculate about the drivers’ personalities. But even after all this, the participants’ judgments of the cars’ speeds were still accurate and there was no tendency to overestimate the speed of the BMW. This was true even though participants had earlier made the kind of assumptions about the two drivers that you might expect — for example, that the BMW driver was more aggressive and reckless.”

Interestingly, it wasn’t until the third experiment that any predicted stereotype that BMW drivers drive faster was activated. A day after they viewed the speed clips, subjects were asked unexpectedly to recall the speeds. “In this case, the BMW’s speed was estimated to be significantly faster (56 mph) than the Polo’s (50 mph), even though both cars were actually traveling at the same speed (60 mph).”

I was reminded of work I had somewhere about stereotypes and “priming” — in some cases invoking presumed stereotypes seemed to force subjects to work harder to reject them. But when asked “out of the blue,” with no stereotypical context in mind, and perhaps less time or reason to think about the answer, the subjects here seemed to lean on preconceived notions that BMWs are driven faster. Davies’ experiment was meant as yet another calling into question of the reliability of eyewitness testimony, but as in the first experiment, it also shows the variety of ways the world of traffic is not always as it seems.

Posted on Thursday, June 25th, 2009 at 6:33 pm by: Tom Vanderbilt
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The Slingshot Effect

Reader Brad writes in with a query:

I wondered if you could indulge me by trying to answer a question that has long puzzled me; I drive mostly on rural roads, and not infrequently must follow a slower car until the opportunity to pass occurs. Often, as I pass I notice the other car speeding up slightly — at least 5–8 mph it seems over its previous speed; almost a magnetic or slingshot effect. I have even noticed that at times I do it myself, involuntarily, as I am being passed! Is this a recognized phenomenon with its own name?

Has anyone else experienced this? One answer may be that the driver being passed has simply lost track of his speed, and being passed suddenly alerts them that they may be driving slowly; speeding up may be a sort of panic response. Another answer is that the sight of being passes awakens some competitive impulse, a version of the “territorial defense” mechanism theorized by Barry Ruback — even if the territory is abstract road space, and the person passing in this case is actually not competing for the same resource, given that they’re in the opposing lane. Or maybe they’re just playing chicken.

In Traffic I note a strange, somewhat related version of this phenomenon, which I call “passive-aggressive passing” — someone bullies you out of the left-lane, you dutifully get over, and they then pull in front of you, and drive slower than they were when they were on your tail. It’s as if all they wanted was to get you to pull over.

But I have no doubt there may be less than noble motives at work in these cases. I myself am guilty of doing something like the following: I will be driving along (in say the middle lane) when I notice someone coming at a high speed on the right side. It seems as if their intent is to cut in front of me, in the small space I have left between myself and the vehicle in front of me. Annoyed by this person’s behavior — the idea that they may pass close to me at a high speed, perhaps forcing me to brake — I have at times slightly accelerated, so that I move closer to the vehicle that is ahead of them in their own lane. The result is that they must hit the brakes, and try something else.

Immature? Perhaps. Or maybe it’s simply pro-social altruistic punishmenthomo reciprocans.

Posted on Tuesday, June 16th, 2009 at 8:10 am by: Tom Vanderbilt
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The Sense of Being Stared At (in the car)

As we’re on the topic of curious psychological effects, have you ever, as a passenger in a car, stared to the side, at a driver in the neighboring lane, and suddenly had them turn to face you?

This is a game I sometimes play when bored in the back of a taxi, and it can be quite disconcerting. I have often wondered: Am I simply remembering with greater frequency and fidelity those times when somebody actually looked back, and forgetting all the times they didn’t, invoking a sort of memory bias (e.g., because I think that people stare back I am primed to remember the times they actually do)?

The rogue psychologist Rupert Sheldrake has explored the “eyes in the back of the head” phenomenon (or what he calls the “non-visual detection of vision”) in his book The Sense of Being Stared At, which has occasioned a good amount of critical commentary. But, as Sheldrake has noted, the feeling that this sense exists is quite strong:

Most people have had the experience of turning round feeling that someone is looking at them from behind, and finding that this is the case. Most people have also had the converse experience. They can sometimes make people turn around by staring at them. In surveys in Europe and North America, between 70% and 97% of the people questioned said they had had personal experiences of these kinds (Braud et al., 1990; Sheldrake, 1994; Cottrell et al., 1996).

When I do in this car, of course, I am more properly considered to be alongside the other person, or just behind, so it’s perhaps not as much as a “non-visual” detection as a peripheral detection. But still, it seems quite powerful — what would make someone take their eyes off the road and return my glance? (another proviso here is that they may simply have been turning to look at my car, out of idle curiosity). Is it some primitive apparatus for detecting hazards? Is it that incredibly powerful ability we humans have (and which the non-human primates do not) to detect, and make, eye contact?

What’s interesting too is what happens once that driver in the other lane meets my eyes. Often, they look a bit startled, or uncomfortable, and I myself try to look away, having been uncomfortably caught out. This too has been examined by psychologists, as this piece in Scientific American notes:

In one version of the experiment, the research assistant pulled up in his motor scooter next to a car waiting at a red light and stared expressionlessly at the driver until the light turned green. In another version, the research assistant stood on the street corner, turned to face an approaching pedestrian, and again stared expressionlessly at this person’s face for an uncomfortable length of time.

As predicted, being stared at prompted people to ‘flee’ measurably faster than not being stared at. In the case of the motor scooter, car drivers who were in the staring condition stepped on the gas pedal harder when the light turned green than those in the control condition, as measured by the length of time it took them to cross the intersection. Likewise, pedestrians who were stared at also picked up their step.

In any case, I’m curious to hear from readers: Do you ever notice this effect? Are there any other explanations I’ve left out?

Posted on Wednesday, May 20th, 2009 at 10:48 am by: Tom Vanderbilt
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Bad News for Traffic Signal Manufacturers

From the Times of London, a story that seems “ripped from the pages” of Traffic.

The always good transpo correspondent Ben Webster asks:

What would happen if traffic lights were suddenly switched off? Would there be gridlock or would the queues of frustrated drivers miraculously disappear?

People in London are about to find out the answer in Britain’s first test of the theory that removing lights will cure congestion.

For six months, lights at up to seven junctions in Ealing will be concealed by bags and drivers will be left to negotiate their way across by establishing eye contact with pedestrians and other motorists.

The reason for the trial was pure accident:

Ealing found evidence to support its theory when the lights failed one day at a busy junction and traffic flowed better than before. Councillors have approved a report which recommended that they “experimentally remove signals since experience of signal failure showed that junction worked well.”

Of course, careful attention will have to paid to safety results, particularly with pedestrians (the piece refers to some new mid-block crossings but one has to entertain the idea that these treatments may reduce pedestrian’s perception of safety and thus, potentially, one’s inclination to walk). The one day of outage could have represented a novelty effect. But the interesting thing about these novel treatments is that they are often done with much more care and concern than the standard “out of the book” approach that is applied automatically.

Ealing Council believes that, far from improving the flow of traffic, lights cause delays and may even increase road danger. Drivers race towards green lights to make it across before they turn red. Confidence that they have right of way lulls them into a false sense of security, meaning that they fail to anticipate hazards coming from the side. The council hopes that drivers will learn to co-operate, crossing junctions on a first-come first-served basis rather than obeying robotic signals that have no sense of where people are waiting.

(Horn honk to Prashanth)

Posted on Saturday, May 2nd, 2009 at 3:22 pm by: Tom Vanderbilt
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Theater of Illusion

One of my favorite blogs, Cognitive Daily, is launching a new feature, Cognitive Monthly, which features a long single-subject article. They’re hoping you’ll like the article enough to contribute a small fee.

The first month’s entry is about a subject that relates peripherally to something I discuss briefly in Traffic; i.e., the relationship between the way we see the world and how that world is captured in film (and by the way there’s another great NYAS event forthcoming this week that deals with that very topic). The piece is titled “The Illusion of Theater” and it, in their words, “covers the remarkable science behind what theatrical professionals seem, to laypeople, to do intuitively: create an environment that encourages us to believe that what we see on stage is a true representation of reality.”

In any case, here’s a sample of what the kind of stuff you’ll find in the piece:

How exactly does the music affect perception of a scene? In 2000, Marilyn Boltz conducted an extensive study to try to answer that question. Boltz wanted to know whether music alone could change the way viewers thought about a scene in a film, and furthermore, whether it could actually affect viewers’ memory later on. She showed viewers three ambiguous scenes, from Cat People, Vertigo, and the TV show The Hitchhiker, and played either “positive,” “negative,” or no music to accompany the scenes.

Boltz found that when viewers watched Malcolm McDowell and Nastassia Kinski talk in a benign scene from Cat People accompanied by positive music, they saw McDowell primarily as “kind/caring,” “loving,” or “playful.” When the negative music was played, he became “crazy/deranged,” “evil,” manipulative,” “controlling /possessive,” and “mysterious” (and this is without seeing him turn into a black leopard and rip someone’s arm off). When asked to predict what would happen next, viewers who had never seen the film and who saw the version with positive music (“Blossom Meadow” by George Winston) thought that McDowell and Kinski would have a happy life together and possibly fall in love.

Viewers who instead saw a version with negative music (from Rubycon by Tangerine Dream — of Risky Business fame) thought McDowell would “harm,” “kill,” or “do supernatural harm” to Kinski. The results were similar for scenes from Vertigo and The Hitchhiker. So music matters, whether we’re watching a bad ’80s HBO series or a Hitchcock classic—or a play by the son of a tenant farmer
in central England.

Posted on Friday, May 1st, 2009 at 2:42 pm by: Tom Vanderbilt
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Even the Above-Average Suffer From the Lake Wobegon Effect

A new piece in Science by John D. Lee, “Can Technology Get Your Eyes Back on the Road,” had a number of interesting things about it but I particularly liked this fact about the “above-average driver” effect:

“Another survey found this superiority bias persisted even with expect police drivers when they rated their ability relative to that of their peers.”

It could be, of course, that we just have trouble thinking in terms of groups.

Posted on Friday, May 1st, 2009 at 9:10 am by: Tom Vanderbilt
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Is this Love or Congestion?

Sydney’s transport commissioner was recently talking about congestion in his city and made this analogy:

“It’s like being in love. If you think you are in love, you are in love. If you think you are in traffic, you are in traffic.”

He was trying to make the point that people tend not to think of traffic in relative terms. To wit: “It’s no good for me saying, ‘Oh, it’s much worse in New York or Paris.’ ”

I’m not sure if this is some kind of power-of-positive thinking exercise, in which case the next time you encounter heavy traffic you could repeat the following mantra: “I am not in traffic. I am not in traffic.”

It also hints at how elusive traffic is; sure, the engineers have their “level of service” designations and all that, but there is no universal standard for “bad” or “good” traffic. People in North Dakota might get itchy when they fail to make it through a traffic light on the first pass; a person in L.A. might feel lucky to make a left turn on the second arrow. And when one hears figures comparing early 20th century urban speeds in London or Manhattan being the same as they are now, should this even be termed as congestion or “bad traffic” and not simply be the default operating condition?

(thanks Richard)

Posted on Monday, April 27th, 2009 at 8:14 am 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 Dilemma Zone

“Let us consider for a moment you are driving down the road and approaching a signalized junction. The scene in front of you is a dynamic one and is constantly evolving. The light is at present green but of course this may change. The intersection is also currently clear, but of course this may also change. Now let us run the scenario forward. As you approach the actual crossing, the visual angle between the traffic light and the forward view across the junction begins to increase. There comes a point in time where one cannot see both together. This is not a divided attention issue or one or foveal versus peripheral field of view, it is a simple question of structural interference, the driver’s eye cannot see both at the same time. The design efforts of traffic engineers in terms of sight lines, seek to reduce any such occurrences of ambiguity, and on most occasions they are very successful. However, let us consider this example as one of inherent ambiguity. Where is the driver to look? If you look at the light to see a possible change, one cannot look at the intersection and vice versa. The pragmatist will say that by the time the light changes, the junction should be free. However, the simple fact is that driving presents many such ambiguous situations in which, whatever “correct” action one is actually accomplishing, there is another equally “correct” action that one must neglect. What of distraction in such circumstances? Can we say the driver involved in a collision in such circumstances is distracted and is not driving with due care and attention?”

That’s one of the many interesting bits of a paper by P.A. Hancock, M. Mouloua, & J.W. Senders, “On the philosophical foundations of driving distraction and the distracted driver,” in a recent book titled Driver Distraction: Theory, Effects, and Mitigation.

Posted on Wednesday, February 25th, 2009 at 4:43 pm by: Tom Vanderbilt
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9/11 and the Subsequent Rise in Traffic Fatalities: More Exposure, or More Stress?

There have been a number of papers that have argued that have identified a post 9/11 uptick in traffic fatalities, theoretically based on a rise in driving, itself motivated by a fear/dread of flying (most notably, Gerd Gigerenzer, 2004, “Dread risk, September 11, and fatal traffic accidents,” in Psychological Science).

A new paper, “Driving Under the Influence (of Stress): Evidence of a Regional Increase in Impaired Driving and Traffic Fatalities After the September 11 Terrorist Attacks,” by Alexander J. Rothman, et al., also in Psychological Science, comes to a rather different conclusion.

“Although we confirmed that U.S. domestic air travel decreased significantly following September 11,” the authors write, “our analyses did not support the claim that there were notable increases in driving miles and in traffic fatalities across the United States after that date. In fact, total U.S. driving miles in the post-September months in 2001 did not differ significantly from total U.S. driving miles in the same months in 1999 and 2000, and the observed increase in total U.S. driving miles in October through December 2001 appears normative when examined within broader historical trends. The number of fatal traffic accidents in the United States did increase, albeit only marginally, in the 3 months following September 11, but there was no evidence of an overall increase in traffic fatalities.”

They did find one change amidst the data, however: “We did obtain evidence that the terrorist attacks had a systematic, but localized, effect on traffic fatalities.” The “localized” effect was on the Northeast, the region arguably the most directly impacted by the September 11th attacks. “Our analysis revealed a significant increase in traffic fatalities in the Northeast in the final 3 months of 2001.”

They continue: “To examine regional differences in traffic fatalities further, we used alcohol- or drug-related citations and reckless-driving citations as two behavioral indicators of psychological distress… [W]e found a significant increase in the number of alcohol- or drug-related citations issued in connection with such accidents during the last 3 months of 2001, but only in the Northeast. The concurrent regional increases in traffic fatalities and in alcohol- or drug-related citations lend support to our second hypothesis—namely, that behaviors impairing the quality of driving increased in those regions most affected by the terrorist attacks, and may have contributed to the observed elevation in percentage of traffic fatalities. This effect is consistent with other findings indicating that exposure to traumatic events is associated with an increased use of psychoactive substances, especially alcohol (e.g., Chilcoat & Menard, 2003; Pfefferbaum & Doughty, 2001)…”

Interestingly, they found the rate was the effect was highest in New York State, though they caution that “that meaningful operationalization of geographic proximity can be complicated and remains a task that is beyond the scope of this article.”

So, if correct, the study implies that it wasn’t a mere affect of people driving more miles to avoid airplane travel, but that their behavior on the road had in some way changed (one Israeli study found a similar increase in fatal crashes in the days following suicide bombings). My initial instinct was to think that a rise in drunk driving crashes might make sense from the perspective that more traffic enforcement officials were pulled off the roads and put into other duties in the wake of 9/11, although that wouldn’t necessarily explain the rise in citations. Another issue is to break down more specifically what kinds of roads people were driving on after 9/11, as Michael Sivak and Michael Flannagan have done, although, interestingly, this seems to potentially add weight to this study: Sivak and Flannagan found “the largest increase [in driving] occurred on local roads, not interstate highways that would be the main alternative to flying. Local roads, both urban and rural, accounted for 45 percent of the increase in traffic deaths.” Presumably, people swapping out flights for long-haul driving would be on those interstate highways, not local roads. As Rothman and his colleagues caution, “the rates of fatal traffic accidents, and hence fatalities, may have increased in the Northeast after the attacks as a result of more people driving in unfamiliar areas because of road closures and detours.”

Lastly, one can’t be certain that aggressive driving or impaired driving is a sign of “psychological distress.” Still, the pattern, localized in time and place, seems very real and suggestive.

(Horn honk to Shirl)

Posted on Monday, February 16th, 2009 at 3:24 pm by: Tom Vanderbilt
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I Respect Your Right to Drive Like a Maniac Down This Street, But…

Since so many drivers seem to lack any other kind, Needham, Massachusetts is hoping to appeal to their “emotional intelligence,” reports the Boston Globe.

As is so often the case, the community in question is trying to get people to drive more slowly on neighborhood streets with schools and children. The typical signage seems to do squat. As the story notes, “The idea is that seeing a child’s handwriting and drawing will make parents relate to the sign in a way they never would with an impersonal version.” In other words, it’s not the voice of the impersonal state, but a child — and how many SUVs loaded with parents’ own offspring are barreling down that road?

Interestingly, this idea did not stem from traffic engineers. Writs the Globe: “She said the novel approach came out of a conference she attended last year, when Daniel Pink, best-selling author of “A Whole New Mind,” talked about using so-called right-brain skills like empathy to communicate more effectively – and ultimately to be more successful.”

Pink himself “came upon the idea by accident while visiting a New York museum with his wife and three young children. The family took a break from touring to get something to eat at the museum cafeteria. ‘The line is just outrageously long,’ Pink recalled. ‘And I’m all stressed out about that because we don’t have a lot of time, and I don’t want to waste my time at this beautiful museum waiting for a grilled cheese sandwich.” Then he saw a sign that read, “Don’t worry. This line moves really quickly.’ Pink said he immediately felt much calmer and it made his entire experience at the museum better.’

This may all be a bit too soft for the New Yorker raised on “Don’t Even THINK of Parking Here” and its ilk. And I’m not sure about the legibility of those signs (then again, legibility is only half the issue). But I’m all for unconventional approaches, and this one seems an interesting parallel with the U.K.’s “road witch” trials and David Engwicht’s “intrigue and uncertainty” ethos, the idea that the “outdoor living room” of a residential street, one that shows signs of life, might be as or more effective than anonymous, disregarded signs. I’m also not sure about the ‘novelty effect,’ but in any case it will be interesting to see how it plays out (the town is trying the ’empathetic’ signage for other purposes, as well). I like the idea of simply posting images of huge sets of eyes with any traffic message, as psychological experiments have shown how eye contact (not necessarily “real” eye contact) improves cooperation.

Part of me can’t help but to look at those “child-like” signs, meant to engender feelings of empathy for the nearby children, and think they almost say more about the drivers. We often hear about how children are “unpredictable” and do things like cross at inappropriate moments, but to look at the behavior of drivers through these school areas it is they who seem to be behaving without the appropriate amount of control and risk-awareness. How can a person drive in such an environment without the understanding that they are in the presence of unpredictability? (of course, with issues of speed, one tends to only hear from drivers about how they feel they are traveling at a speed that is safe for them, without taking into account the ethical dimension of how their behavior raises the risks to others). To take the analogy further, how many “children” do we see out on the roads, hostile to being reigned in, thinking that parental rules don’t apply to them, selfish to the extreme (swap a toddler’s crying for the horn), angry when their toys are taken away (how dare you remove parking spots!).

What do y’all think — more carrot, less stick? Or the reverse? Or a whole new way of thinking about the problem?

Posted on Tuesday, February 10th, 2009 at 10:13 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.

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