Archive for the ‘Traffic Psychology’ Category

The Psychology of Aggression on the Highway

From Florida, where this sort of thing seems to happen inordinately, comes a classic tale of armed “road rage”:

Two men arrested in what could have been a disastrous road-rage shootout on Interstate 95 Sunday offered an insight into the psychology of aggression on the highway when each sought police to report the other’s actions, experts said…

The fact that each sought to report the other points to the extreme perspectives that can appear in a road-rage confrontation, said Dominik Guess, a University of North Florida associate professor of social and cognitive psychology.

“We don’t see the world how it is; we see the world through our own eyes,” said Guess, who studies decision-making as part of his research. Neither of the men probably believed they were wrong, he said.

In the end, however, both were arrested.

Posted on Monday, February 9th, 2009 at 2:40 pm by: Tom Vanderbilt
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The Problem With ‘Shovel-Ready’ Thinking

Via Popular Mechanics:

There are no specific parameters or requirements that define shovel readiness. But according to civil engineers, the idea behind this new buzzword could help scuttle the stimulus bill’s highly publicized, though secondary, goal of infrastructure reform. At issue is that 90-day restriction stipulated by Congress, an even narrower window than the bill’s original 180-day limit. “They’re well intentioned, and they know their infrastructure sucks, so they’re trying to do immediate reactive management to what is a very deep, endemic problem,” says Robert Bea, a professor of civil and environmental engineering at the University of California, Berkeley. “If you want to patch some potholes in the road, this is a good program. But if you’re hoping for anything long-term with this approach, throw away all hope. It can’t happen.”

The programs that would meet the bill’s 90-day restriction are, for the most part, an unappealing mix of projects that were either shelved after being fully designed and engineered, and have since become outmoded or irrelevant, or projects with limited scope and ambition. No one’s building a smart electric grid or revamping a water system on 90 days notice. The best example of a shovel-ready project, and what engineers believe could become the biggest recipient of the transportation-related portion of the bill’s funding, is road resurfacing—important maintenance work, but not a meaningful way to rein in a national infrastructure crisis. “In developing countries, there are roads that are so bad, they create congestion, because drivers are constantly forced to slow down,” says David Levinson, an associate professor in the University of Minnesota’s civil engineering department. “That’s not the case here. If the road’s a little bit rougher, drivers will feel it, but that’s not going to cause you to go any slower. So the economic benefit of those projects is pretty low.”

I would only disagree in that NYC, there are some roads that are so bad they make you slow down, but the benefit here is that it acts as passive (and inexpensive) traffic calming.

Posted on Monday, February 9th, 2009 at 11:50 am by: Tom Vanderbilt
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Why We Think White Stripes on the Highway Are Shorter Than They Really Are

In Traffic I mention one of the most common, and surprising, ways we are fooled by what we see on the road: White stripes. I was asked by one engineer to guess how long they are, and I was more than a bit off in my estimation.

It turns out I’m not alone. A fascinating new study, headed by Dennis Shaffer, assistant professor of psychology at Ohio State University’s Mansfield campus and appearing in Perception & Psychophysics, asked a group of subjects to recall from memory — as well as look at a recreated “stripe” and during an actual drive — the length of the dashes. The most common answer was two feet — which is interesting considering the federal guideline calls for ten feet.

The finding holds implications for traffic safety. Each dashed line measures 10 feet, and the empty spaces in-between measure 30 feet. So every time a car passes a new dashed line, the car has traveled 40 feet. But in this study, people consistently judged the lines and the empty spaces to be the same size, claiming that both were two feet.

“This means that to most people, 40 feet looks like a lot less than 40 feet when they’re on the road,” Shaffer said. “People cover more ground than they think in a given period of time, so they are probably underestimating their speed.”

Interestingly, Shaffer began his pioneering research when the federal guideline was for fifteen feet, which has since shrunk. But no matter.

“Wherever the researchers went, they found all lines to be close to the federal guidelines of the time. In Arizona in 2000, for instance, some lines were 16 feet long instead of the expected 15.

But even back then — when the federal guideline was 15 feet — people still thought of lines as measuring only two feet.

What’s going on?

One possible explanation: as we drive, we look out far ahead the car for safety reasons, so the only lines we really see are faraway lines that look small.

Even though lines appear to expand as a car passes by, drivers can’t safely notice that effect. Rather, the first line we can comfortably look at while driving safely is some 120 feet ahead — the fourth line ahead on the road. So perhaps we think that all lines are as small in reality as that one faraway line appears to be.

But why are so many people consistently wrong, in exactly the same way?

As to why everyone’s estimates were consistent in every experiment, Shaffer suspects that the answer has something to do with how our brains perceive geometry. Engineers design roads, buildings, and public spaces using Euclidian geometry — the system of lines and angles first described by the ancient Greek mathematician Euclid. But this study and previous ones suggest that our brains perceive objects in a non-Euclidian way.

Might this cause a paradigm shift in the schools of highway engineering, a ‘non-Euclidian’ revolution? Maybe we shouldn’t use lines at all, and instead use random geometric patterns — Mandelbrotian fractals? — to delineate highway lines. In any case, the study is useful in quantifying what most engineers, and readers of Traffic, already know. Shaffer, meanwhile, carries on.

In the future, Shaffer will examine how people perceive the size of lines that are oriented at different angles — as if seen by a driver approaching a bend in a road — and how our perceptions affect our ability to judge the steepness of hills.

Posted on Tuesday, February 3rd, 2009 at 9:27 am by: Tom Vanderbilt
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Green Wave Blues

One of my personal urban pet peeves is that the traffic signals on a street like New York’s Fifth Avenue, on which a majority of users are pedestrians, seemed timed in such a way to interfere as much as possible with smooth ambulatory progress. Seriously, I feel like I have to stop at every single light on Fifth.

From the invaluable Streetfilms comes a look at what would happen if a street like Valencia in San Francisco had its signals timed such that cyclists had a green wave. What about cars, you ask? Isn’t that anti-car-ism? Well, actually, as San Francisco Streetsblog points out: “Recently, the San Francisco Municipal Transportation Agency (MTA) found that during peak commute times vehicles run more efficiently when signals are timed at the speeds they actually travel during congestion — 12 to 15 mph — rather than the current 25 mph.” Not to mention that cyclist signal compliance rates will inevitably rise. On streets to which you’re trying to attract cycles, why not offer the carrot instead of merely the stick? Synchronization, in a grid city, has its natural limits but it’s certainly worth favoring certain modes on particular streets.

I often find some of the most hazardous urban driving behavior to be people accelerating between lights, or emerging from a pack of congestion. The question is how to get drivers to stick to speeds that are lower overall, but actually promote smoother, more fuel-efficient driving. ISA (intelligent speed adaptation) is probably the most far-reaching tool, but in some ways a political non-starter in the U.S. (for now, at least). I suspect that merely telling drivers through signage that the only way to get a row of greens is to drive 15 or 20 mph will somehow not work (the average driver is an incredibly opportunistic, short-range planner, only concerned with getting to the next red light as fast as possible).

Posted on Monday, February 2nd, 2009 at 4:24 pm by: Tom Vanderbilt
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If You See Something, Say Something

One theme explored in the book is the usefulness of feedback to the driver, as well as the occasional unwillingness for a driver to want to hear this “feedback” (what we colloquially call ‘back-seat driving’). Some curious process occurs between man and machine by which they suddenly feel themselves above criticism, incapable of making an error, that they alone understand the road and traffic conditions. For anyone to suggest otherwise risks earning their wrath, despite the fact that studies have shown non-teen drivers with passengers are involved in fewer crashes than those flying solo.

A forthcoming study out of Kenya again hints at this dynamic. A pair of researchers at Georgetown University equipped a number of matatu buses, the private fleet of microbuses typical in many developing nations, with posters urging passengers to “heckle and chide” the driver if he is driving too recklessly. Rather like the recent hotline numbers at football games in which patrons can report drunken and abusive fans around them, the posters work on the idea that while everyone may be gripping the seat as the driver slaloms around town, no one individually feels empowered to speak up (a campaign in Ireland called “He Drives, She Dies,” urged a similar thing for female passengers in their boyfriend’s cars — it turns most who are killed or injured do so while passenger to a male driver; research apparently showed that most didn’t want to urge the driver to slow as they feared they would actually increase their speed if they did so).

The research — I’ll be posting again on the paper — apparently shows that buses in which the posters were displayed were involved in fewer crashes than those in which no posters were displayed (the buses account for some 20% of crashes in Kenya).

(Horn honk to Marginal Revolution and Shanta Devarjan)

Posted on Monday, February 2nd, 2009 at 3:18 pm by: Tom Vanderbilt
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More Distracting Fun From the DFT

An interesting play-it-at-home distracted driving challenge from the DFT. I missed five questions and my pedestrian spotting was off by one.

Obviously we aren’t asked to assign values to pedestrians while driving, nor hit space bars; but then again, we don’t have to steer, brake, turn, merge, check mirrors, or do anything else in this simulation (mind you, many U.S. drivers wouldn’t stop anyway at those marked crosswalks, unless there was a pedestrian in dead center).

(hat tip to Mind Hacks)

Posted on Wednesday, January 21st, 2009 at 7:58 am by: Tom Vanderbilt
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Change Blindness

Transport for London has already riffed on “inattentional blindness,” without giving props to Daniel Simon — but hey, it’s for the public good, right? But I hadn’t yet seen this take on “change blindness.”

I won’t give it away but I did very poorly.

Posted on Friday, January 16th, 2009 at 12:04 pm by: Tom Vanderbilt
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The Enigma of Arrivals

Yesterday morning found me at a TRB panel, “Building the 21st Century Transportation System,” moderated by NYC’s own Janette Sadik-Khan. There were a number of interesting details offered — e.g., that J.S.K. had played rugby at Occidental College (she was abroad the year Barack Obama was there) a good skill set I think for navigating Gotham politics; or that Portlanders drive 4 fewer miles per day than other places in the U.S.; or that Seattle is high on the safety benefits of “advanced stop bars” — but one small anecdote that caught my attention in particular was offered by Fred Hansen, of Portland’s Tri-Met.

Talking about the city’s “Transit Tracker” program, which allows people to get real-time info on bus arrivals via their cell phones, Hansen mentioned a study that had been done in the U.K. of a similar program. What was noteworthy was that people using the service felt that the bus service itself had improved, that more buses were running, that they were running closer to schedule, even though none of this was empirically true.

I have a particular interest in the fluid nature of time, and the way travel, queuing, and even routing can play additive and subtractive games with this. Paco Underhill, for example, notes that people who wait in airport lines overestimate the time they waited by some 50 percent. I’ve also seen it noted that a train trip with a transfer feels longer to people than it really is, that people overestimate the time it will take to walk somewhere and underestimate the time it will take to drive somewhere. Of course, one of the masters of managing time is Disney, with its posted wait times (just posting the time makes it feel shorter for people) at queues, wait times which are then inflated — so the payoff at the end is even better: That wasn’t long at all!

The lesson here, I suppose, is that perception can be just as important as reality in crafting the “customer experience,” a lesson that applies as much to public transit as it does to the Magic Kingdom.

Posted on Wednesday, January 14th, 2009 at 5:00 pm by: Tom Vanderbilt
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‘A Prevailing Sense of Tragedy’

A friend writes from Trinidad to alert me that the book had been referred to in yesterday’s Trinidad Guardian, albeit under an unfortunate set of circumstances: The road death of a promising young boxer. The editorial follows:

“Refresh message of road safety

The news of the death of boxer Jizelle Salandy and the injuries sustained by national footballer Tamara Watson only add to a prevailing sense of tragedy on the roads of Trinidad and Tobago. Just a few days before, an automobile crash threatened the careers of two of this country’s track stars, Richard Thompson and Monique Cabral. In the first week of the new year, there are already two fatalities on the books and the loss of Salandy, a young boxer with an unblemished record of wins, is particularly painful. The Arrive Alive campaign has done much to bring the issue of road safety back into public discourse, and to heighten awareness of hot-button issues like drunk driving.

If, however, there is anything at all that a troubled nation can take away from the disturbing news of the last week, it is the need to drive the message of careful and defensive driving deeper into the public psyche. Among its many warnings about crime in Trinidad and Tobago, the UK’s Foreign and Commonwealth Office cautions: “The standard of driving in Trinidad and Tobago is erratic. Road accidents leading to fatalities are a regular occurrence.” On his blog, Tom Vanderbilt, author of the book “Traffic: Why We Drive the Way We Do (and What It Says About Us), noted about his visit to Trinidad and Tobago in December, 2008: “According to Thursday’s Trinidad Guardian, in a little box headlined ‘Mr. Death’ showing an image of the Grim Reaper, there have been over 250 (actually 226 at that point) road fatalities this year in T&T.

“By just one comparison, Northern Ireland, which this year had one of its safest years ever, has around 120 fatalities—with a population some 600,000 larger. The reasons are not hard to imagine: There are many two-lane, non-divided highways in the country, which people drive at routinely high speeds (life seems relaxed everywhere except the roads).” The reasons for the high incidence of accidents and road fatalities are well known; a culture that endorses speeding and a lax appreciation of the rules of the road and the lingering machismo of drinking and driving. The tragedy of Jizelle Salandy’s passing and the near misses that have spared Thompson, Cabral and others who have survived mishaps on the road recently, should serve as a caution for the upcoming Carnival season, which will run for potentially dangerous weeks.

While previous efforts at road safety education have been enthusiastic and laudable, real changes in national attitudes to road safety will only come when people start talking to each other about the consequences of dangerous driving behaviour. Those conversations need to begin among young people, the sector of society most likely to be out late at night, driving fast cars and in a state of diminished judgment. Stakeholders interested in minimising risk on the road and Government agencies and ministries with a focus on the young should encourage popular young personalities to make road safety and sound judgment when driving in risky situations part of their conversations with their audiences, colleagues and friends.

Young people with a leadership role in communities, schools and groups should be encouraged to set an example and spread positive word of the value of key safety issues like designated drivers, defensive driving techniques and the need to respect the safety of passengers over matters of ego or style. Through our youth newspaper, GIENetwork, the Guardian stands ready to play our part in delivering a message of safety and due diligence on the road to young people vulnerable to the temptations and enthusiasms of driving during the Carnival season. A reduction in the number of people killed on the nation’s roads requires an all-out national effort that touches everyone in this society, in order to forestall the loss and injury of valuable young lives.”

While I’ll all for the messages of attitudes and personal action in the editorial, there is one other aspect that deserves note, namely this fragment from a Guardian article:

“Frederick said that upon reaching vicinity of the NP overpass at Sea Lots, Port-of-Spain, Salandy hit a culvert and smashed head-on into a concrete pillar, dubbed the killer pillar. People who fell victims to that pillar in the past included Ram Kirpalani and chief immigration officer Joseph Bodkyn. Members of the Emergency Health Services (EHS) arrived promptly and pulled out a bloodied Salandy who was still conscious. She was taken to the Port-of-Spain General Hospital, but died around 8.29 am, while undergoing emergency surgery.”

I don’t know the road in question, but under modern safety engineering such an obstruction near a road intended for higher speeds — particularly one that already killed at least two other “boldface” names — would certainly be dealt with some Brifen wire, etc.

Posted on Wednesday, January 7th, 2009 at 3:43 pm by: Tom Vanderbilt
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Give and Take

In Traffic I talk a bit about the curiously positive feeling you can get when you are “let in” by a driver with a friendly wave — perhaps, as some have suggested, triggering some inherent impulse towards reciprocal altruism, even though we’ll never see that driver again. Conversely, if that same driver rudely cuts in front of you with nary a glance, you might have a desire to punish them in some way, as if they would somehow learn not to mess with you the next time (even if there won’t be a next time). One question is: Were these feelings of positivity and negativity essentially equal, even if the value of the “transaction” (i.e., the right of way) was the same?

A new study by Boaz Keysar and colleagues at the University of Chicago, titled “Reciprocity is Not Give and Take: Asymmetric Reciprocity to Positive and Negative Acts,” (pdf here) published in the December issue of Psychological Science, based on a number of trials of experimental “giving” and “taking” games in the lab and on the street, suggests that we are much more willing to “escalate” our response in the face of “negative reciprocity” (e.g., when we’re cut off) than we’re willing to reward someone in the face of positive reciprocity. Indeed, our perception of the exchange is skewed by this dynamic. “Because giving appears to be inherently more generous than taking, an objectively more selfish giver can sometimes be seen as more generous than an objectively selfless taker.” The authors conclude by suggesting a new mantra: “You scratch my back, and I will scratch yours, but if you take my eye, I will take both of yours.”

In a University of Chicago release, Keysar made an explicit parallel to traffic:

“For instance in driving, if you are kind and let someone go in front of you, that driver may be considerate in response. But if you cut someone off, that person may react very aggressively, and this could escalate to road rage.” (of course, one problem is that it’s objectively more difficult to reward someone in traffic — you can drive courteously or safely, but that’s what you’re supposed to already be doing — than it is to find ways to harass them).

Things get worse when the offender doesn’t realize how much their offense is being felt by their victim. “The one receiving the slight cannot imagine that the slighter lacks that appreciation. And so it goes, because of such differential perception, they respond more and more strongly. Small slights could escalate to unbelievable, irrational feuds.”

Which might lead, just spitballin’ here, to something like this:

Posted on Tuesday, December 23rd, 2008 at 8:37 am by: Tom Vanderbilt
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Crosswalk Psychology II


The earlier poll I mentioned over at Cognitive Daily has concluded, and the results are in.

As Dave Munger writes, vis a vis the above chart: “Overall, the chances of stopping varied a lot from situation to situation. Was there a marked crosswalk? Did the pedestrian appear to be looking at the car? Was she on the left or the right?”

The results seem to conform to what I’ve seen in pedestrian/crosswalk studies — i.e., that drivers are more likely to stop for a marked crosswalk, when the pedestrian is on their side of the road, and when they’re actually in the street, as opposed to standing on the curb. Signalling intention, in short, is a good way to gain right of way; whether the pedestrian was looking at traffic or not looking, interestingly, didn’t seem to tilt strongly either way.

Munger also notes: “One more thing: I’m not sure if the responses to this study truly reflect real-world behavior. Nora and I took the photos for this study on a road where the speed limit was 35. There was quite a bit of traffic, and so we spent a long time standing on the roadside waiting for traffic to clear. Not one driver stopped for Nora.” In other words, the poll respondents’ willingness to stop did not conform to the actual willingness of drivers to stop, which reveals one of the inherent weaknesses of self-reported data in traffic psychology.

For an interesting take on how pedestrians and drivers behave in crosswalks, and their understanding of the actual law (generally less than you might think), see “What They Don’t Know Can Kill Them“, by Meghan Fehlig Mitman, UC Berkeley Traffic Safety Center, and David R. Ragland, UC Berkeley Traffic Safety Center.

The key takeaway: “Results confirm that a substantial level of confusion exists with respect to pedestrian right-of-way laws. This confusion was exacerbated by intersections which had unstriped, or unmarked, crosswalks.”

Posted on Saturday, December 6th, 2008 at 3:25 pm by: Tom Vanderbilt
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‘Hands Free’ Is Not Brain Free

I’m slow to post on this, but I’ve finally gotten around to reading a new cell-phone driving study from the indefatigable David Strayer and colleagues from the University of Utah’s Applied Cognition Laboratory, via The Journal of Experimental Psychology: Applied.

With all the usual caveats (a small sample of student-aged drivers in a simulated driving environment), this study is of particular interest for addressing a question one often hears: How is talking on a phone while driving any different than talking to a passenger?

Among other things, test drivers were asked to exit a highway at a rest stop area under different conditions — while on the phone, while a passenger was present, etc. The researchers found that “drivers in the cell phone condition were four times more likely to fail task completion than drivers in the passenger condition.” (these were the socially sanctioned, but arguably no less distracting, ‘hands free’ phones, by the way).


They write: “On the strategic level of performance, cell phone drivers performed poorly at the navigation task. Two nonmutually exclusive explanations can be provided for this deficit: First, drivers conversing on a cell phone may experience problems with keeping the intention of exiting at the rest area in working memory, or second, drivers may not sufficiently process information from the driving environment (exit signs). Some support for the latter hypothesis comes from studies demonstrating inattention blindness in cell phone drivers (Strayer et al., 2003).”

What’s particularly interesting here is the way the conversation also changed with the cell-phone. Drivers made fewer references to traffic on the cell phone (because the person on the other end isn’t sharing the experience, or presumably interested in sharing it), and what’s more, actually started to speed up their conversation, even as it grew less multi-syllabic: “Also, quite surprisingly drivers conversing on the cell phone increased their production rate when talking on the cell phone, which is contrary to the predictions of the modulation hypothesis. More interesting, this happened even as those drivers in the passenger condition tended to reduce their production rate.”

The speech was getting simpler, in other words, even as it grew faster.

Drivers on cell phones, the author speculated, “may have attempted to dominate the conversation to avoid having to engage in speech comprehension, whereas with in-vehicle partners, it may be easier to relinquish control, given that the partner can be relied on to accommodate with his or her contributions.” (I’ve overheard quite a few cell-phone conversations where it seemed the caller was trying to dominate the conversation).

As study co-author Frank Drews told the Salt Lake City Tribune:

“It’s crazy. They talk faster. It’s quite counterproductive for driving safely,” Drews said. “There is an obviously malevolent influence.”

And, of course, it depends on who the passenger is: “For example a passenger who is too ‘supportive’ by constantly commenting and directing attention in an overcontrolling fashion has a potentially negative impact on performance.” (what I call the ‘Hyacinth Bucket syndrome’).

See the video here.

Posted on Thursday, December 4th, 2008 at 4:33 pm by: Tom Vanderbilt
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Crosswalk Psychology

Cognitive Daily is running (until today) an interesting poll that shows a variety of situations with pedestrians in or near the crosswalks, and asks the user in which conditions they would be likely to stop. This picks up on a theme of a number of previous applied psychology experiments, which I described in the book, that reveal how we tend to comply with traffic laws rather situationally — rather than obeying them whole-cloth, in any condition (researchers have, for example, tested people who appeared to be blind, with a white cane, versus others, and found higher yielding rates; similar studies have been done with eye-contact, gender, among other variables).

Give it a try.

[p.s.: If that street is really marked for 45 mph, that’s really high for a residential area with pedestrians].

Posted on Thursday, December 4th, 2008 at 8:44 am by: Tom Vanderbilt
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The Hazards of Silence

There have been any number of studies — the work of Warren Brodsky, for example — investigating the potentially harmful effects of driving while listening to loud music (particularly of a certain tempo).

But a new paper by Mark Horswill and Annaliese M Plooy, at the University of Queensland, “Auditory feedback influences driving speeds,” published in the latest edition of Perception, talks about the risk of a car being too quiet.

As any reader of car reviews will note, reduced “cabin noise” is always seen as a positive feature. Reduced noise is thought to mean more “comfort” for the driver, though there are more spurious reasons being put forth; Horswill quotes one automotive engineer who notes that “automobiles will have to become significantly quieter, keeping the noise out so passengers inside can enjoy the latest advances in communications and entertainment technologies.” (that’s right, cars are now intended to be rolling phone booths!)

The problem is that noise — road noise, engine noise, etc. — acts as a form of feedback, helping to increase the driver’s situational awareness (described by Neville Moray as “shorthand for keeping track of what’s going on around you in a complex, dynamic environment”).

In his study, Horswill had drivers look at a variety of filmed driving scenes, which were played at a variety of different speeds and under different levels of audio “stimulus.” He found that ” reducing noise made vehicle speeds appear slower than they were.” When the decibel level was reduced by 5, the drivers thought they were moving 5 kph slower than they really were. You may be thinking that people can simply use the speedometer as the more accurate form of feedback, but previous studies have found people consult their speedometers rather rarely (“approximately 12 times over the course of a 6.4 mile, or 10.2 km, route” — this during a trial whose very task was to keep a set speed). The difference in speed may also seem minor, but given that small increases in speed at higher speed led to much higher increases in crash risk and damage, this may not be as minor as it seems.

An observation once made in another paper (“The ironies of vehicle feedback in car design,” in Ergonomics by Guy Walker, et al.), that “drivers’ self-awareness of the state of their own situational awareness appears to be very poor,” also seems to apply in this case: Drivers did not realize how the lack of auditory cues was influencing their own perception. To be cue-less is to be clue-less.

Posted on Wednesday, November 19th, 2008 at 10:45 am by: Tom Vanderbilt
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Risky Business: Speeding and Trading

It’s hardly news in the traffic psychology world that people who routinely speed fall under the category of what are called “sensation-seekers.” But it’s always interesting to see just who those people are, and how this behavior correlates with other areas of their life.

A study by Mark Grinblatt, a professor of finance at the University of California, Los Angeles, and Matti Keloharju, a finance professor at the Helsinki School of Economics, titled “Sensation Seeking, Overconfidence and Trading Activity” (available here), gets at that question in an interesting way.

They had access to an interesting data set: A record of investing behavior among Finnish households that had, scattered amongst its sub-categories, the number of speeding tickets those households received. And they found an interesting relationship: “Each additional speeding ticket tends to increase turnover by 11%.” In other words, the people who sped the most, traded the most.

The economists were really looking to find evidence of whether behavioral attributes could explain trading volume, but the finding is just as relevant for driving. Whether it was down to sensation-seeking or, perhaps, overconfidence, the riskiest investors took the most risks on the road. And given that this was Finland, where speeding tickets for violations over 15 kph are related to one’s income, the risks one took could bear a high financial (and personal) cost. Interestingly, those who traded most didn’t see better performance than those who traded less (not to mention all the money they probably lost to speeding tickets). And it will surprise no one that “sports cars,” as a variable, were more linked to the most active traders, though not as much as speeding tickets.

Posted on Thursday, November 13th, 2008 at 4:43 pm by: Tom Vanderbilt
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Are Narrower Lanes More Dangerous?

An interesting article in the St. Louis Post-Dispatch notes that crashes have increased on I-44 after they were narrowed to 11 feet wide, from 12 feet. They were narrowed to add a fifth lane and increase capacity in the wake of the temporary closure of another road, Highway 40. This is of interest because a key congestion-fighting measure that has emerged for an era of scarce highway funds is increasing the efficiency of existing infrastructure (e.g., by carving out new lanes).

The article notes: “The increase in overall collisions is typical whenever lanes become narrower, according to the Federal Highway Administration. The skinnier the lane, the less room there is for error. It’s why the federal government recommends that lanes on interstates be 12 feet wide.”

But there are some caveats to consider, within the same article:

1.) “Volumes on I-44 have gone up 10 percent to 30 percent during rush hour since the Highway 40 closures, according to the Transportation Department.” If the crash figure is 27 percent higher than the comparison period, it’s hard to know what percentage of crash increase has to do with narrower lanes, and which has to do with increased volume (or some other factor).

2.) Fatal crashes have actually gone down. Does that make the entire facility more or less safe?

3.) The speed limits have been reduced, but driver compliance is an issue. “You look at them and think, ‘OK, there goes another idiot,'” Stremlau said. “It’s that way on any highway. It’s just exacerbated by the narrower lanes.” Safety depends on context, and the real issue seems to be driver speed rather than lane width.

4.) The types of crashes mentioned, multi-car rear-end collisions, have little to do, theoretically, with lane width. “The bulk of them,” a police officer said, “are caused by tailgating.” Tailgating is a speed issue, not an issue of proximity to a neighboring vehicle. The police even came up with a novel suggestion: “Despite more traffic, police say the additional lane can make the interstate feel less congested, thus encouraging drivers to floor it.”

5.) There may be less room for error, but that may make drivers pay more attention, thus canceling out the increased risk.

Ezra Hauer has researched this issue rather extensively, and reports on the complexity of the issue here. Note that some crash types have been found to increase over 11 feet.

Of one study, he writes: “They also note that “narrowing of lanes to 11 feet (or occasionally 10.5 feet) while maintaining shoulders did not change accident rates.” Based on the review of several projects in California the authors note that: “. . . higher accident rates had not materialized several years after lanes were narrowed and left shoulders were removed . . .”

Posted on Wednesday, November 12th, 2008 at 6:02 pm by: Tom Vanderbilt
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The Behavioral Revolution

Reading David Brooks’ elegant summation of how behavioral psychology and economics can help explain the dynamics of the financial crisis — to explain, as he puts it, “why so many people could have been so gigantically wrong about the risks they were taking” — I couldn’t help but think of another area rife with questions of risk and decision-making, namely ‘the way we drive.’

Whether from personal on-road experience, or from reading studies, or from examining in-car footage of crashes and near-crashes, I am often struck by how often people seem to put themselves, and others, at great risk. Following closely at high speed on the interstate, or driving fast through a neighborhood street, they act in a way that suggests they believe that nothing could go wrong, or that they would be in control if it did. Over time, this behavior is typically rewarded, perhaps through sheer luck, until the ‘black swan’ event that they never expected actually happens. Then, as is often the case, begins a process of denial, an attempt to assuage the cognitive dissonance that has come between the image of themselves as a good and cautious driver and an event that was ‘beyond their control.’

Some quite literal connections can be drawn between the behavior of traders and the behavior of drivers. For one, both activities are prone to the ‘above-average effect’ — studies have shown how both large groups of traders and drivers define themselves to better than average. What’s also interesting is the gender question; research has also shown men seem to be more susceptible to the above-average effect. As Brad Barber and Terrence Odean showed in their paper Boys Will Be Boys, a study of a large brokerage house found that men made many more trades than women, per account, seemingly indicating a heightened sense of confidence, but that their portfolios on average earned less than women. Given the male dominance in the trading sector, it’s not hard to extrapolate these findings to the larger financial crisis. It also need hardly be pointed out that men are involved in more fatal crashes than women — overconfidence mixed with a greater propensity for risk-taking.

Another connection is the way we act on the information we perceive. “And looking at the financial crisis,” writes Brooks, “it is easy to see dozens of errors of perception. Traders misperceived the possibility of rare events. They got caught in social contagions and reinforced each other’s risk assessments. They failed to perceive how tightly linked global networks can transform small events into big disasters.”

This passage reminded me of a recent conversation I had had with a journalist in Abu Dhabi, who was telling me about the massive, fatal chain-reaction crashes that have occurred on fog-bound highways there. Fog is a classic perception problem: Differences in contrast affect how we perceive speed. Moving through fog, drivers actually feel as if they are moving more slowly than they are. So they continue to drive fast, much faster than they should. They may also drive close to the vehicle in front of them, thinking, falsely, that seeing the taillights of the driver ahead is safer than not seeing anything. All this is fine until the rare event happens, and that ‘tightly linked’ network, full of people reinforcing each other’s risk assessments and acting on what they think is sufficient information (but which may disguise hazards around the bend), find themselves in a calamitous crash.

Behavioral psychology isn’t part of the driver’s ed curriculum, of course, but there’s no reason it shouldn’t be, given that attitudes and behavior are as, if not more, important than driving skills per se. And the simple vision test that’s given is fine for testing the strength of one’s vision, but left unmentioned is the idea what we see of the world does not always represent the world as it is.

Posted on Thursday, October 30th, 2008 at 9:36 am by: Tom Vanderbilt
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Word of the Day: Bikeism

Adrian, a psychology grad student in Australia, wrote in with mention of a disturbing episode in Australia, recounted here, of a car driver going after some cyclists in an “Around the Bay Day” event (for charity, mind you).

What one editorialist also found objectionable, however, was the link at the bottom of the page where readers could vote on that day’s opinion question. The question was: Are cyclists responsible road users?

Not really the first question that comes to mind after reading the original article (I’m almost afraid to know what the answer was). As the writer put it, “OK. If those hooligans had bowled over a bunch of grannies going to church, would readers be having their say on whether senior citizens are responsible road users?” A more contextually appropriate question to vote on, in my opinion, would have been: Should drivers who commit what is essentially aggravated assault with a deadly weapon have their driving rights permanently revoked? (uh, yeah)

The writer went on to coin the word “bikeism” to describe the dynamics he thought were at work — tarring an entire class of people with the extreme acts committed by a few (or a stereotypical image of that behavior). “Unfortunately, many motorists who don’t ride bikes and don’t understand cycling seem to think that all cyclists are ego-driven menaces who run red lights.” (more…)

Posted on Tuesday, October 28th, 2008 at 3:35 pm by: Tom Vanderbilt
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A Car Named Sue

Via the Boston Globe Ideas section. If you believe what college undergraduates have to say on questionnaires extrapolates at all to the real world. And that people still do things like name their car once they graduate.

“YOU BETTER WATCH what you say about my car. She’s real sensitive.” Nevertheless, unless you run across a car named Christine, there’s nothing to worry about, right? Think again. A study by psychologists at Colorado State University found that almost half of the more than 200 drivers surveyed in a college class had assigned a gender to their car (more females than males) and that over a quarter had given their car a name, including ones like Lolita, the Sweat-box of Death, and Jolly Green Giant. Drivers who had assigned a gender to their car – regardless of whether it was male or female – indicated a greater tendency to driving-related aggression and anger. The students were also asked to assess their car’s personality. The personality ascribed to the car was typically somewhat different than the driver’s, and knowing this invented personality improved predictions of the driver’s aggressiveness.

The study is: Benfield, J. et al., “Driver Personality and Anthropomorphic Attributions of Vehicle Personality Relate to Reported Aggressive Driving Tendencies,” Personality and Individual Differences (January 2007).

Posted on Monday, October 27th, 2008 at 6:35 pm by: Tom Vanderbilt
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Cogitive Dissonance

In Traffic I spend a fair amount of time talking about the “myth of multitasking,” and my basic riff on talking on a phone (doesn’t matter if it’s hands-free or not) and driving is that you’ll be doing one or the other — and perhaps both — less well. By how much depends on the driving and it depends on the conversation.

NPR took a novel approach to demonstrate the mechanics of distraction: Rather than looking at a driver, they asked a professional musician to play piano while being asked to do other things.

To wit:

“For over an hour, we tasked Frasch with playing a range of pieces, some he knew and some he had to sight-read. While he was playing, we asked him to multitask. Sometimes the additional work was simple. For instance, Frasch has no trouble talking about his childhood while playing a Bach minuet. But when the challenges took more brain power, it was tougher for Frasch to answer questions and play the piano at the same time.”

Is it just me or was he actually not even that smooth on this part?

It gets worse:

“So we took it up another notch. We gave Frasch a piece of music he’d never seen before, a fast-tempo number. While he was sight-reading, like a driver navigating an unfamiliar route through a big city, we asked him to do a math problem:

“What’s 73 minus 21?”

Frasch played on while he thought through the problem out loud. He hit a few wrong notes on the keyboard before coming up with the right answer: 52.

A multitasking driver might have hit something else. Just says the pianist, who was already working hard to follow the music, simply couldn’t handle something else that required real thinking.”

As one of the commenters notes, this guy is a professional, someone who’s practiced for countless hours. Imagine by contrast the “average” driver and the sheer range of novel events that can happen on the road.

(thanks to Peter Warnock)

Posted on Thursday, October 16th, 2008 at 9:05 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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Attitudes: Iniciativa Social de Audi
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Metropolis and Mobile Life
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