Archive for July, 2008

Murder at the Traffic Circle

I wasn’t quite sure what could top, in terms of senseless road depravity, the story, from Los Angeles, of the driver who attacked a pair of cyclists with his car (it was his second reported altercation).

But then I read about the case of the Seattle man who was killed while tending to the flowers in the traffic circle outside his house, apparently by some passing drivers who took issue with the safety cones he had temporarily put up while watering. The man, a Vietnam vet, had himself lobbied for the circle after a car had struck his house.

Posted on Wednesday, July 16th, 2008 at 7:49 am by: Tom Vanderbilt
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The purposeful white-glowing pedestrian

I was just reading a nice little write-up of Traffic in O: The Oprah Magazine, and I noticed it was just adjacent to a similar plug for Joseph O’Neill’s fine novel Netherland.

The pairing may have been accidental, but I couldn’t help notice, when reading Netherland, a subtle fascination with traffic. There’s a scene at the DMV, for example, and Chuck Ramkissoon takes the narrator on a series of less than altruistic driving lessons. There’s talk of “crazed traffic diagonals” and “triangular traffic islands.”

My favorite bit, though, was this short description of the comparative physiognomy of “green men”:

“At a certain point, Chuck grabbed my arm and said, ‘Let’s cross now,’ and he trotted quickly across the avenue as a surge of traffic came roaring up. He had, I realized, waited for a moment when the pedestrian light showed the fierce red hand, and then taken his chance. Evidently he felt this gave him an edge—and it did, because it meant that, walking on down Sixth Avenue, he and I were signaled forward at every cross street by the purposeful white-glowing pedestrian whose missionary stride was plainly conceived as an example to all (and whom I cannot help contrasting with his London counterpart, a green gentleman undoubtedly rambling with his golden retriever).”

He’s right about this, Chuck is: Typically the only way for a pedestrian to not encounter a “don’t walk” sign on the next block is to cross against the light on the previous block. The lights are timed for cars, not pedestrians — even though pedestrian traffic is often much heavier in New York City.

Posted on Tuesday, July 15th, 2008 at 3:06 pm by: Tom Vanderbilt
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More Bad News for the Auto Industry

“Percentage of U.S. homeowners who reported last year that they had bought a car using a home-equity loan: 27.”

Via Harper’s Index, August.

Posted on Tuesday, July 15th, 2008 at 6:46 am by: Tom Vanderbilt
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Mind-bending Illusions on LSD

The recent discussion in the press of illusory speed bumps in Philadelphia reminded me of a conversation I had a while back with the Chicago Department of Transportation. For years, the curve at Oak Street on Lake Shore Drive has been something of a crash hot-spot. It’s within the typical engineering guidance for acceptable curves, but given that drivers on LSD tend to treat the Drive as an urban expressway rather than the boulevard it really should be, there’s been a consistent crash problem, particularly on rainy days and the like.

CDOT responded with a series of gradual alterations. They made the lane markings more distinct. They made the curve warning signs bigger. Then they added flashing lights. Drivers still weren’t getting the message. So CDOT got perceptual. (more…)

Posted on Monday, July 14th, 2008 at 2:17 pm by: Tom Vanderbilt
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When Slower is Faster

One theme that I found myself returning to again and again in Traffic is the often counterintuitive notion that “slower can be faster.” This idea comes up in any number of traffic (and network) situations — ranging from “ramp meters” at highway entrances, to the “speed harmonization” techniques used on motorways like the M25 in England, to individual drivers pacing themselves to avoid “driving into the jam,” to the practice (espoused by hyper-milers and eco-drivers) of not racing needlessly up to red lights, to getting rid of traffic lights and replacing them with roundabouts, which often seem slower but on average process more traffic than conventional intersections. As a study by Australia’s Monash University, titled “The Impact of Lowered Speed Limits in Urban and Metropolitan Areas” notes, even a lower speed limit can paradoxically produce faster traffic (particularly in “medium” congestion). The reason: “A lower speed limit may actually reduce overall travel time by allowing a more harmonic traffic rhythm.”

I was intrigued to come across a lo-fi, but effective, demonstration of this principle on YouTube (where a traffic subculture flourishes), using Martin Treiber’s excellent traffic simulator. As someone who constantly finds himself zipping past drivers at the lights— drivers who had moments before blazed aggressively past me — this is a nice example of how our own driving style helps contributes to traffic problems.

Posted on Saturday, July 12th, 2008 at 4:43 pm by: Tom Vanderbilt
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Fueling Up, Fueling Down

The Economist notes:

“For years it seemed that American consumers’ demand for liquid fuel was price inelastic—whether it was to drive their cars or get their brains going in the morning. Yet $4 seems to have been the price at which demand becomes elastic, for both petrol and a frothy latte. As a result, baristas at Starbucks coffee shops around America are starting to get a taste of what it feels like to be a carworker in Detroit.”

I wonder what the actual relationship between gas prices and Starbucks’ performance is — are their sales down more in places where people drive more? Are things worse at Starbucks with drive-throughs than those without?

I find the magazine’s comparison interesting in light of the old saw that says coffee is the world’s second most-traded commodity — right behind oil. I know which form of sludge I’d rather cut back on (it’s not the one you drink).

Posted on Friday, July 11th, 2008 at 11:44 am by: Tom Vanderbilt
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On “Distracting Miss Daisy”

A few readers have asked me what I thought of “Distracting Miss Daisy,” an article by Duke University psychologist John Staddon in the current Atlantic (the full text is past the jump).

To briefly summarize, Staddon, who has driven in both the U.K. and the U.S., thinks American drivers suffer from a surfeit of traffic signs and speed limits. “The more you look for signs, for police, and at your speedometer, the less attentive you will be to traffic conditions.” He argues this helps explain the superior traffic safety record of the U.K.

On the whole, I was quite sympathetic to the spirit of the article, which was lively and well-argued — indeed, it visits a number of themes and places mentioned in my book (which has, for example, a section called “The Trouble with Traffic Signs”). His line, “we spend a lifetime on the roads after we get our licenses, and we’re being trained by our experiences every day,” could serve as a summary of Traffic. And as someone who recently took, as an experiment, a U.K. driving test (I’m writing an article about this), I’ve got my own opinions about comparative driving culture in the U.S. and the U.K., some of which are in line with Staddon’s point of view.

There were a few points in the article I thought deserved discussion, however.

1.) He says that in his experience, people “drive faster” in Britain. This just shows, I suppose, how subjective experience is. I challenge anyone to spend a week taking black cabs in London, and a week taking Yellow Cabs in New York City, and report a higher average velocity in the former. Also, the default speed limit in England of “lit, urban roads” is 30 mph. I’ve been in U.S. cities, in fairly urbanized areas, with (unobeyed) 40 mph limits. While we’re on the subject of limits, he does not mention in his piece the widespread deployment of speed cameras and red-light cameras in the U.K., two technologies which would seem “designed to control drivers and reduce their discretion” — a charge he makes against U.S. traffic safety efforts.

2.) He rightly invokes “risk compensation” in discussing why safety improvements in cars do not often produce the desired results: The safer people feel, the more riskily they act. But a bit later, he notes, “a particularly vexing aspect of the U.S. policy is that speed limits seem to be enforced more when speeding is safe.” (e.g., a sunny day). But is this not a form of risk compensation in itself? After all, most crashes occur during the day, during normal weather — the times we no doubt feel safer. As Leonard Evans notes in Traffic Safety, nearly 85% of fatal crashes happen on dry roads. There’s no such objective, quantifiable thing as a “safe” speed in traffic — plenty of people have died driving at the proper “design speed” of roads, while many children have been killed in driveways by cars going under 5 mph. The only thing we scientifically know is the higher the speed at which you collide with something, the greater the physical damage, and greater the risk of dying.

3.) And on the subject of speed, I am skeptical of Haddon’s claim that “looking at your speedometer” is an important form of distraction on the roads. First, I’m not sure how much time is actually spent looking at speedometers (in one study, drivers were asked, after they went through a slow school zone, how fast they were driving, and their estimates were wildly low). The second is that experienced drivers typically have a lot of spare cognitive workload, plenty for quick glances at gauges — and any minor distraction from a speedometer pales with the demands of, say, cell-phone conversations.

4.) I was interested that he notes that he finds roads “generally wider” here, which one might think would make things safer. In my U.K. driving test, taken in suburban London, I was quite surprised to find how often, on small residential streets, I had to pull over to let another car by. In general, I found road geometries tighter (and I was driving a fairly small car). But this is one of the ongoing debates in traffic safety: Making roads wider means you have less chance to bump into someone, but it also means you’re likely to drive faster. The experiments in which traffic control have been taken away (e.g., Drachten, Poundbury) only work because they are happening at very slow speeds, where the logic of human interaction, and not traffic engineering, take over.


Posted on Thursday, July 10th, 2008 at 10:11 am by: Tom Vanderbilt
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Is the ‘Michigan Left’ Right for America?

Left turns at intersections are the bane of traffic. They impede traffic flow (a “protected” green arrow holds up the majority of the intersection for a minority of drivers), UPS drivers’ routes are programmed to avoid them, and they’re dangerous for drivers (who often have trouble judging the speed of oncoming drivers, or have their view obstructed in determining whether it’s safe to cross) — not to mention pedestrians, who typically have the “Walk” signal when cars have a left-turn signal (and, because of the aforementioned problems, cars may only be paying attention to pedestrians at the very last moment).

Yesterday, John J. Miller asked me about a regional specialty in the world of traffic, the so-called “Michigan left.” Having spent some time in the environs of the Motor City, I had a passing familiarity with the system, but had sort of filed it away in my brain — and didn’t bring it up in the book. But he raised a very good point: Why isn’t it used elsewhere?


Posted on Wednesday, July 9th, 2008 at 2:20 pm by: Tom Vanderbilt
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The Traffic Guru

That’s the title of an essay I’ve written, reflecting on the ideas and legacy of Hans Monderman, the famous Dutch traffic engineer (now there’s an unlikely phrase) who died earlier this year. The piece, which builds upon some material in the book, is just out in the new Wilson Quarterly.

Posted on Wednesday, July 9th, 2008 at 11:53 am by: Tom Vanderbilt
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The MPH Illusion: How We Misjudge Time Savings on the Road

Imagine there were two roads that could be fixed to improve drivers’ travel times. Imagine also they’re the same length, but have different average speeds.

Fixing the first road will see drivers’ speeds increase from 40 kph to 50 kph.

Fixing the second road, meanwhile, will see drivers’ speeds go from 80 kph to 130 kph.

Given that the construction costs would be the same to fix each road, which road would you choose to improve? Which would result in more time saved (and, hence, more social benefit)?

If you’re a regular, math-challenged sort like me, you probably picked the second option. But apart from some minor rounding differences, the amount of time saved for each is actually the same.

This example comes from a fascinating new paper, “Driving Speed Changes and Subjective Estimate of Time Savings, Accident Risks and Braking,” by Ola Svenson, head of the Risk Analysis, Social and Decision Research Unit at Stockholm University.

I’m admittedly someone who has trouble computing things like how much time an increase in speed will save — once you get me off the nice 60 mph mark (a mile a minute), things get a little fuzzy. But now I’ve found I’m apparently not alone. When Svenson asked this to a group of respondents, a majority thought the 80 to 120 kph option was better. The reason, he speculates, has to do with a sort of “proportion heuristic,” an effect that’s been found in many other contexts (the work of Daniel Bartells is instructive here); in what he calls a “ratio rule,” we’re biased by the ratios in speed changes, rather than employing the actual, more complex formula.

What this means on the road is that we may underestimate time savings of increases in lower speeds and, perhaps more importantly, overestimate the time savings we gain when we begin to accelerate from an already high speed. He also looked at estimations of crash risk and braking distance as it applies to speed — both of which are non-linear — and found similar mis-estimations. He notes: “Intuitive arguments for higher speeds may be biased.”

Astute readers will note the curious echo here of another study, the so-called MPG illusion, by Duke University researchers Richard P. Larrick and Jack B. Soll, which found that increases in MPG from 16 to 20 can save as much fuel, relatively, as going from 33 to 50 mpg.

Previous research has found that we tend to overestimate trip lengths, and we think the waits at things like traffic lights were longer than they really were. The lesson in Svenson’s new paper, I suppose, is that that a car’s instrument panel is more complicated than it appears.

Posted on Tuesday, July 8th, 2008 at 3:50 pm by: Tom Vanderbilt
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“Cars kill more people than handguns do…”

That line comes from Dan Gardner’s Risk: The Science and Politics of Fear, a wonderfully provocative, engagingly written study of the psychology of risk. It’s not available quite yet in the U.S., but you can preorder the book from Amazon in the U.S. (where it has a slightly different title and cover).

One of the already shopworn canards of election season here in the U.S. is the refrain “we live in a dangerous world,” or “we live in dangerous times.” No one ever goes to make the point that underlies Gardner’s book: Just how less dangerous the world now is (for those in the developed world, at least). A baby born in England in 1900, he notes, could expect to live to an average of 46 years. Her great-grandchild, born in 1980, would see an average life expectancy of 74 years. The great-great grandchild, born in 1980 — almost eight decades of expected life. While on the subject of England, he notes the murder rate in the Middle Ages there was fourteen times what it is now.

I could go on quoting interesting things from the book, but as one chapter of Traffic focuses on risk on the road, I found one of Gardner’s footnotes particularly interesting. Describing a media panic that emerged in the wake of two tragic incidents in Canada in which drivers were killed by truck tires that had come loose on the highway, he writes: “Reporting proliferated and even trivial incidents in which no one was endangered made the news. It seemed the roads were in chaos. New safety regulations were passed and, just as quickly as it appeared, the crisis vanished.”

But what was the result of all the attention? Was a real risk brought to a close, or did a remote risk continue to strike more or less at random? The number of incidents, and fatalities, notes Gardner, more or less fluctuated up and down, following no real pattern (save perhaps the regression to the mean), with no fatalities one year, two the next. As he writes, “before the panic, tires came loose occasionally and there was a tiny risk to motorists. The same was true during the crisis and afterward. All that changed was appearance and disappearance of the feedback loop.” For a while, it seemed as if there was a “flying truck tire” epidemic on Canadian roads, but it was merely an artifact of disproportionate media attention — attention which may have been better paid to the larger sources of risk, like alcohol and speed.

Posted on Monday, July 7th, 2008 at 11:06 am by: Tom Vanderbilt
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“July 4th Is the Most Dangerous Day to Drive…” And the Problem With Saying That.

With the Fourth of July holiday weekend upon us, you’ve probably already been exposed to one of the holiday’s traditions, as familiar as fireworks or hot dogs: The dangerous driving warning.

On the one hand, there is good reason for this. July 4th is, statistically, the deadliest day on the road (see this study, for example, which notes it was the day with the highest traffic fatalities in the U.S. from 1978 to 2002). In many years, particularly when the 4th is on, for example, a Saturday, July 3rd ranks right behind it. Roughly half the crashes involve alcohol.

But now for the problem. As the New York Times pointed out a few years ago, the death toll on July 4th is high, compared to an average day, but it’s not really that high at all — just 6% higher — compared to the one day of the week that is decidedly not average: Saturday. When you factor in the greatly increased highway traffic, the 4th may actually be safer than the average Saturday, for which we receive no warning.

Perhaps all the warnings and advisories keep the day from being more dangerous than it would be, but this raises the question of the frequency of the warning. As David Klein and Julia Waller observed in a 1970 report for the Department of Transportation, “the ‘holiday death toll’ may give drivers an unjustified feeling of anxiety on holiday weekends and a false sense of security on weekdays.” Yes, the 4th is statistically dangerous, but not much more so than the average Saturday, and it is not orders of magnitude away from the average weekday; essentially, the amount of media coverage of dangerous driving during holidays is well out of proportion with the incidence of dangerous driving spread throughout the year.

This year, of course, the high price of gas and the economic slowdown are showing a silver lining in lower traffic fatalities across many states. If the pattern holds, this will be a “safer” July 4th than typical if only because of reduced exposure.

So here’s my message: Drive safely this Fourth of July, but drive safely on July 5th, July 6th, and so on …

Posted on Thursday, July 3rd, 2008 at 9:17 am by: Tom Vanderbilt
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Accidental Vanity Plates

Do you ever, as I sometimes do, notice a license plate that seems poised somewhere between the randomness of the state DMV and a full-on vanity plate? And you wonder for a moment whether the driver is trying to send some oblique message (perhaps overpaying for a rather weak vanity plate), or whether you’re reading too much into the humble tags, conspiracy-theory style? Sometimes what might seem inconsequential to someone might be very meaningful to someone else; hence the “lucky number” plates in China, where “AC6688” went for nearly $10,000. I’ve had rental cars that began with some suggestive group of letters, e.g., “RU,” or “G7,” and I always wondered whether others saw the glimmers of meaning. After all, we spend a lot of time looking at license plates in traffic.

But now I’ve learned, via Roadguy, that seemingly meaningless configurations can have a way of suddenly becoming meaningful. To wit, some 10,000 plates in North Carolina seem to begin with the three-letter designation: WTF. The DMV’s own website contains this little example of license-plate bingo gone awry. Now, the folks at the DMV are expert at screening out potentially offensive vanity plates, but they certainly can’t predict the future, and could not have known that that might become a very meaningful acronym from the world of texting. They’re offering to replace them.

Now it’s got me in a panic. My own plate begins with “CUY.” Do fellow drivers think I’m paying vehicular homage to the Andean delicacy? Or will that someday become a contentious acronym (for, I dunno, “Coyote Ugly Youth”)?

I’m curious as to what other examples of “accidental vanity plates” might be out there in the real world, and I’ll send a signed copy of Traffic to the reader who sends a photo with the best example to I’ll post the winner a bit down the road. CUL8R…

Posted on Tuesday, July 1st, 2008 at 4:09 pm by: Tom Vanderbilt
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Significant Seven

I’m quite honored to be among Amazon’s “Significant Seven” — i.e., the Best Books of the Month.

The 40% discount now makes the book (assuming free shipping) cost less than four gallons of gas. Perfect ‘staycation’ reading!

Posted on Tuesday, July 1st, 2008 at 11:02 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:

For publicity inquiries, please contact Kate Runde at Vintage:

For editorial inquiries, please contact Zoe Pagnamenta at The Zoe Pagnamenta Agency:

For speaking engagement inquiries, please contact
Kim Thornton at the Random House Speakers Bureau:

Order Traffic from:

Amazon | B&N | Borders
Random House | Powell’s

U.S. Paperback UK Paperback
Traffic UK
Drive-on-the-left types can order the book from

For UK publicity enquiries please contact Rosie Glaisher at Penguin.

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



July 2008

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