Archive for the ‘Uncategorized’ Category

Bike Tolls on the Triborough

With some out-of-town visitors to entertain, my destination yesterday was (where else!) the MTA’s Transit Museum. There I noticed a small detail that had escaped my notice prior — i.e., the presence of bike tolls on the Triborough Bridge. Can any transpo geeks out there enlighten us as to any more details about this? What was bike traffic like across the bridge when it opened? Was there a special toll booth, or did cyclists merge into a car lane? When was the toll scrapped? And for that matter, when did the (little-observed) policy of cyclists walking their bikes across the bridge(s) come into being?

Posted on Wednesday, May 19th, 2010 at 3:13 pm by: Tom Vanderbilt
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‘It eliminates all diversions, it eliminates all emotions’

Tom Farrant is a photographer in the U.K. who’s been documenting the experience of people in the peculiar form of private space in public; i.e., interiors of cars (viewers of Jacques Tati’s Traffic may recall his montages of a similar variety). The above is a photomontage taken from English motorways. What’s striking, apart from the rather blank (verging to unhappy) expression on most people’s faces, is how many turn to look at the camera (that old “sense of being stared at” trope).

I also couldn’t help think of the song by Black Box Recorder:

The English motorway system is beautiful and strange
It’s been there forever, it’s never going to change
It eliminates all diversions, it eliminates all emotions
(All you got to do to stay alive is drive)

Posted on Monday, May 17th, 2010 at 9:16 am by: Tom Vanderbilt
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Selfish Routing, NBA Style

I wasn’t able to get up to the Sloan Sports Analytics Conference this year (though I wanted to, particularly as there were guys from Chelsea and Manchester United there), but as Traffic had both the Braess Paradox and Tim Roughgarden’s book The Price of Anarchy as touchstones, I was intrigued by a presentation from Brian Skinner, a physics professor at the University of Minnesota, which draws some parallels between network (in)efficiencies in roads and the running of successful basketball plays. The video above gives a short description but there’s more on offer at the paper (behind a pay wall):

Optimizing the performance of a basketball offense may be viewed as a network problem, wherein each play represents a “pathway” through which the ball and players may move from origin (the in-bounds pass) to goal (the basket). Effective field goal percentages from the resulting shot attempts can be used to characterize the efficiency of each pathway. Inspired by recent discussions of the “price of anarchy” in traffic networks, this paper makes a formal analogy between a basketball offense and a simplified traffic network. The analysis suggests that there may be a significant difference between taking the highest-percentage shot each time down the court and playing the most efficient possible game. There may also be an analogue of Braess’s Paradox in basketball, such that removing a key player from a team can result in the improvement of the team’s offensive efficiency.

(horn honk to The Transportationist)

Posted on Friday, May 7th, 2010 at 4:20 am by: Tom Vanderbilt
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Yield, Schmield

When I first glanced at the headline, “GPD tracks percent of cars yielding to pedestrians,” I thought, in my jet-lagged haze, wow, here’s a study comparing GDP rates to pedestrian yielding, and I wondered, what’s the correlation — higher GDP means more driving, more exuberant driving, less yielding to pedestrians? A new kind of Smeed curve?

But it’s actually the Gainesville Police Department that’s been trying to make things better for those on foot — and, say it again, everyone’s a pedestrian, even if just leaving one’s car — and I was particularly intrigued by the updated feedback signs (pictured above).

Needless to say, 52% is pretty pathetic.

Posted on Thursday, May 6th, 2010 at 8:10 am by: Tom Vanderbilt
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On Airport Congestion and City Congestion

The comedian Jerry Seinfeld once observed that “closest thing that we have to royalty in America are the people that get to ride in those little carts through the airport.”

He continued: “Don’t you hate those things? They come out of nowhere. “Beep, beep. Cart people, look out, cart people!” We all scurry out of the way like worthless peasants. “Ooh, it’s cart people. I hope we didn’t slow you down. Wave to the cart people, Timmy. They’re the best people in the world.” If you’re too fat, slow, and disoriented to get to your gate in time, you’re not ready for air travel.”

Now, I do believe these carts have their authentic purpose, though recently navigating the airports of Houston and Atlanta — two travel hubs as sprawling as their host metropolises — I found myself, as I walked, constantly buffeted by their passing presence, or subjected to the very same imperious announcements that Mr. Seinfeld decries (and sometimes they were really quite nasty), and I’d watch as hapless travelers were often forced to execute rapid evasive maneuvers to avoid the onrushing conveyances. And sometimes, looking over, I’d see a boatload of what looked like utterly able-bodied people, looking rather smug. After the fourth “beep beep” in a row I was starting to see the world from Seinfeld’s point of view. Like, who regulates who actually gets on these things?

I thought of this when recently penning a short bit for the New York Times’ “Room for Debate” blog, which discussed the city’s plans to reduce and restrict the amount of vehicular traffic on sections of 34th Street, in favor of creating swifter bus facilities and improved pedestrian access.

The airport courtesy cart is a wonderful way to travel. Who wants to walk Houston’s or Atlanta’s long dendritic corridors (dodging those spillover queues from Auntie Anne’s) when you could be whisked, in comfort if not exactly style, directly from security to your gate? Sure, there’s plenty of mass transit options, like shuttle trains and moving walkways, and there’s always good old walking (which I frankly find a welcome respite after four hours of impersonating David Blaine’s latest act of extreme deprivation in 12F), but who wouldn’t want that private door-to-door ride?

The problem, of course, is that if everyone wanted to travel this way, the airport corridors would quickly bog down in a teeming, thrombosed mass of Lagosian proportions. Airports are able to process huge amounts of people because of mass transit, or because they walk.

And I think there’s something of a metaphor here for the presence of the car in the city of the 21st Century. On 34th Street, as the NYC DOT reports, one in ten people who travel on the street go by car. And yet they are granted an inordinate amount of space, and they exact a toll in time on the vehicles carrying many more people. It’s not difficult to imagine the car, forcing its way through a crosswalk during a right turn (as so many do), as the equivalent of that individual courtesy cart disrupting the larger flow of the stream of airport pedestrians for the sake of its few passengers. Or the driver honking as he passes a cyclist as that shrill cry of “beep, beep, cart coming through” that so vexed Seinfeld. Imagine now if, at the airport, courtesy carts were given wide swaths of real estate in which to navigate, and people on foot were relegated to a smaller, crowded, space, and you have something of an idea of the routine spatial imbalance that exists in New York City.

As with the courtesy cart, the car is a wonderful way to travel — the problem, of course, is that it gets less wonderful with each additional driver. Beep-beep.

Posted on Monday, April 26th, 2010 at 11:32 pm by: Tom Vanderbilt
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Those Who Love Me Can Take the Train

Sorry, I’ve always enjoyed the title of that Patrice Chéreau film and wanted to use it for something, and that’s the best title I could come up in the moment.

In any case, I remember reading (and reviewing) Francis Cairncross’ Death of Distance way back in 1998, and I think I’ve actually flown more miles with each passing year since then. A fact I was reminded of reading Anthony Townsend’s interesting dispatch over at IFTF, particularly this comment, a reprise of an earlier post:

At many times people on one side of the debate or the other have wrongly forecast that one side of this equation would overtake the other – we would see the death of cities, the death of distance, and the end of travel. But what’s important here is that these things happened because of each other, not in spite of each other. This particular kind of presence, international business presence, is facilitated by a hybrid set of infrastructure and human activities – making calls and getting on planes.

Now, today, the Internet, for all its distance-diminishing potential isn’t really breaking this relationship. In fact. much of what we use our network technologies for is arranging travel. If you look in your email in-box or keep a diary of mobile phone calls — a safe bet is that 75-90 percent of the messages are about arranging travel or planning meetings.

I’d say he’s about right on that, at least some days.

This too reminds me of an article I recently saw in some (appropriately enough) in-flight magazine: It was essentially a list of places you just had to travel to before they basically vanished, either ruined by ecological forces or placed in critical endangerment by tourism itself. The tragedy of the commons, Travelocity-style.

Posted on Wednesday, April 21st, 2010 at 2:49 pm 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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High Speed Google Map Chase

Satellite Car Chase from Honest Directors on Vimeo.

The budget for the aerial perspective move chase scene just went down dramatically.

(thanks Alan)

Posted on Sunday, March 21st, 2010 at 8:21 am by: Tom Vanderbilt
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A Ramp All the Way

I was grooving on this almost Ed Ruscha-style illustration (“27 Onramp Configurations”?) in a new paper from David Levinson and Lei Zhang, “Ramp Metering and Freeway Bottleneck Capacity,” in Transportation Research: A Policy and Practice 44(4), May 2010, Pages 218-235.

The findings were sanguine on ramp metering:

Traffic flow characteristics at twenty-seven active freeway bottlenecks in the Twin Cities are studied for seven weeks without ramp metering and seven weeks with ramp metering. A series of hypotheses regarding the relationship between ramp metering and the capacity of active bottlenecks are developed and tested against empirical traffic data. The results demonstrate with strong evidence that ramp metering can increase bottleneck capacity. It achieves that by:

(1) postponing and sometimes eliminating bottleneck activation – the average duration of the pre-queue transition period across all studied bottlenecks is 73 percent longer with ramp metering than without;

(2) accommodating higher flows during the pre-queue transition period than without metering – the average flow rate during the transition period is 2 percent higher with metering than without (with a 2% standard deviation);

(3) and increasing queue discharge flow rates after breakdown – the average queue discharge flow rate is 3 percent higher with metering than without (with a 3% standard deviation).
Therefore, ramp meters can reduce freeway delays through not only increased capacity at segments upstream of bottlenecks (type I capacity increase), but also increased capacity at bottlenecks themselves (type II capacity increase). Previously, ramp metering is considered to be effective only when freeway traffic is successfully restricted in uncongested states. The existence of type II capacity increase suggests there are benefits to meter entrance ramps even after breakdown has occurred. This study focuses on the impacts of ramp metering on freeway bottleneck capacity. The causes of such impacts should be more thoroughly examined by future studies, so that the findings can provide more guidance to the development of ramp control strategies. It should also be noted that both types of capacity increases on the freeway mainline are at the expense of degraded conditions at the on-ramps and possibly arterial network. Therefore, without more comprehensive system-wide analysis, the findings of this paper, though in favor of ramp metering, do not necessarily justify its deployment.

Posted on Wednesday, March 17th, 2010 at 7:39 am by: Tom Vanderbilt
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Hummer Death Watch

Final nail.

Posted on Wednesday, February 24th, 2010 at 4:31 pm by: Tom Vanderbilt
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Leafy Streets

We’ve seen that slime mold can function as an incipient urban planner, but leaves offer lessons too, notes the Economist:

Traditionally, biologists have celebrated the trunk, branch and twig system of a tree as no accident. Many mathematical formulas have suggested it is the best, least wasteful way to design a distribution network. But the very end of such a network, the leaf, has a different architecture. Unlike the xylem and phloem, the veins in a leaf cross-link and loop. Francis Corson of Rockefeller University in New York used computer models to examine why these loops exist.

From an evolutionary point of view, loops seem inefficient because of the redundancy inherent in a looped network. Dr Corson’s models show, however, that this inefficiency is true only if demand for water and the nutrients it contains is constant. By studying fluctuations in demand he discovered one purpose of the loops: they allow for a more nuanced delivery system. Flows can be rerouted through the network in response to local pressures in the environment, such as different evaporation rates in different parts of a leaf.

It’s interesting to think of this configuration vis a vis urban/suburban street networks, when less permeable systems push traffic to larger arterial systems — a benefit for those living in the less permeable areas (say, the second photo above, which I believe comes from a stalled subdivision in Florida), until of course there’s some traffic issue on the main line and less opportunity for rerouting flows. The leaf has no cul-de-sacs, no dead-ends.

Posted on Tuesday, February 16th, 2010 at 10:16 am by: Tom Vanderbilt
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Recall Problems

You may have heard the news: Cars that accelerate inappropriately down local streets, veer out of control on rural highways late at night, fail to brake in time to strike a pedestrian, follow lead vehicles too closely to stop in the event of an emergency, and so on. There was a technical problem in all these cases, but one that, I’m afraid, is difficult to fix with a factory recall, for I’m talking about the human decision-making apparatus. Towards this end Leonard Evans provides some much-needed perspective about the Toyota recalls:

Consider: According to various reports, 19 deaths have been associated with Toyota’s gas pedal problem over the past decade. But over the same decade, a total of 21,110 people have been killed in Toyota vehicles, with an additional 1,261 killed in Lexus cars (based on analyzing 1999-2008 fatality data from National Highway Traffic Safety Administration). Almost none of these deaths had anything to do with technology, faulty or otherwise. Almost all of them were the result of driver behavior.

Even the claim that the 19 deaths were “linked” to the defect in no way implies that it was the main factor.

Seventy years of scientific research has shown that what drivers do behind the wheel is the dominant factor in traffic deaths. Speed, for example, is a critical factor in safety. An almost imperceptible reduction in speed from 52 mph to 50 mph cuts the risk of being killed by 15 percent. That’s more than the risk reduction from airbags.

So if the prospect of a sticky gas pedal alarms you, just slow down a little. The result will be that you are safer with the defect than you were without it.

Obviously, deaths linked to faulty cars are a serious problem, and it’s also clear that if attention is not paid, the safety problems could grow much worse. And still, however, I am struck by the sheer volume of the coverage about Toyota — almost verging on a panic — given the comparative risk posed in the numbers above. The study of risk perception is instructive here: Risks seem to loom larger in our imagination when they are novel, and when they are seemingly out of our control, among a host of other factors. Toyota is certainly novel, and the idea that an accelerator might suddenly activate on its own fills us with much more dread than the calculated decision to drive very fast down a street — itself a risk for the drivers and others but seemingly under one’s own control.

There’s a larger story here too, of course, which I was talking about last week with a writer for the Globe and Mail; i.e., the kind of shattering (or cracking) of a mantle of sheer confidence in not just the Toyota brand but the idea of the modern automobile as more or less infallible. When I think of my MacBook Pro or iPhone, I think of wonderful devices that are also prone to bugs (the later device had to be swapped out three times). But thinking about my Subaru, another incredibly complex device, I basically expect that as long as I take it in for its regular maintenance plateaus, I do not expect to encounter any difficulty on the road (needless to say, the experiences at the Genius Bar and Subaru dealership are distinct; one is tense anticipation as I wait to hear the diagnosis, the other is simply showing up to check off the list). Like many other drivers (or at least I suspect), I barely cracked the owner’s manual (this was studied Talmudically in my father’s era) when I bought the car, and certainly didn’t spend much time under the hood because, quite simply, I wouldn’t have understood much of what I was looking at (nor, for the record, do I take apart the MacBook). One still sees articles in the AAA magazines and the like with “driving checklists,” a tally of things you should do before setting out, but I would guess that very few of us do this, for a very simple reason: It has become an article of faith that the car will perform. This contrasts with the situation when I drove used American cars of 1970s vintage as a teenager, during which I experienced all kind of random breakdowns, faulty gas gauges, blinking ‘check engine’ lights that seemed to come on, as if by a law, late at night far from an open service station.

It’s hard to quantify, but I imagine this sense of the machine’s infallibility has changed the way we operate it. It is known that average speeds and following distances changed over time on certain highways, causing engineers to rework their models, and one of the reasons given is, inevitability: Superior handling and performance of the modern car. In this respect, all the coverage given to Toyota is a good thing — if it serves as a reminder of the risks of the road. If it merely shifts further focus away from driver behavior and onto a large, litigable car-maker, this won’t mean much in the overall picture of traffic safety.

Posted on Monday, February 8th, 2010 at 12:07 pm by: Tom Vanderbilt
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Abu Dhabi Street Design Manual

Writing that “previous design guidance was influenced by documents such as the AASHTO Green Book, which is inappropriate for urban streets where modes of transport other than the automobile are present,” Nelson/Nygaard has made available its Abu Dhabi Street Design Manual, which provides guidance to “design streets that create a safe environment for all users; transition from a vehicle-trip based society to a multimodal society; introduce fine-grained street networks into the existing super-block pattern.”

It is, they suggest, “perhaps one of the most progressive in the world.”

Judge for yourself here.

Posted on Wednesday, January 27th, 2010 at 10:10 am by: Tom Vanderbilt
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Hamilton-Baillie on ‘Shared Space’ in Ashford

The town of Ashford in the U.K. was one of the highest profile experiments in ‘shared space’ when it launched over a year ago. The changes, meant to reconnect the center (severed by a hostile ring road) and make the town feel more ‘town-like,’ were quite radical — removing signals, blurring formal notation of right of way — as well as drawn from more traditional traffic-calming approaches (special pavement treatments). The reaction ranged from skeptical to hostile (Jeremy Clarkson, whose opinion on anything but the braking ability of an E-Class Mercedes should be heeded with a yellow flag, predicted ‘millions’ would die).

Ben Hamilton-Baillie, one of the leads on the project (he appears in Traffic), has sent along a Q&A he did with a local paper on the status of the project after one year. Though such things need continual monitoring, the early prognosis is positive and a sign that fresh thinking in terms of the built environment and accommodating traffic can bring good results.

You can read what Ben had to say after the jump. (more…)

Posted on Wednesday, January 27th, 2010 at 8:21 am by: Tom Vanderbilt
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‘Parking Availability Bias’

Driving home from the Yale event last night (which was packed, and filled with all kinds of interesting traffic types, ranging from Norman Garrick to Anne Lutz Fernandez), as I was listening to various renditions of La Boheme on Doug Fox’s wonderful program (Mr. Fox, I didn’t catch the details on that second act), which I discovered for the first time, a warm presence amidst the eerie fog-tinged, arc-lighted Stygian gloom of I-95, I was thinking back to Donald Shoup’s reply to a question I had posed to him, which itself was related to Brian Pijanowski’s study of parking-lot sprawl in Indiana. Despite a huge and quantifiable overabundance of parking in the county he studied, he was interested to note that people still complained “there wasn’t enough parking.”

I asked Shoup, who of course from the groves of academe has helped ignite a quiet but fomenting revolution in parking policy, to what extent this question of perception in the parking equation had been studied or quantified — keeping in mind that perception is a crucial, if often under-appreciated part of the traffic/planning nexus (e.g., commute times, etc.). One part of Shoup’s answer stuck with me: He talked of studying a parking garage in West Hollywood. On the bottom floors, there were cars, and in the empty spaces, plenty of oil stains to indicate past users. On the upper floors, he noted, it looked as if the spaces had never been graced by a single car. And yet the word from drivers was that there was ‘nowhere to park.’ But the problem, Shoup noted, is that drivers’ perception parking supply is informed by the parking spaces they can actually see. Call it “parking availability bias” (ode to Tversky and Kahneman). And the spaces that are most easily seen, of course, are curb spaces, hence the importance of rational market pricing policies to ensure turnover and vacancy. A few empty spaces (15%) can go a long way.

This perception is a powerful force and leads cities into all kinds of policies that turn out to be misguided and rife with unintended consequences; take the “free holiday parking” approach. Towns hoping to lure shoppers downtown, away from the big boxes, offer up free parking. But beware the power of incentives: Given that many of the best parking spaces in front of local businesses are often occupied (it happens right here in Brooklyn) by the store keepers themselves, the free parking bonanza ends up actually enticing local employees (who would have parked elsewhere or not driven) to grab some free real estate for the day — leaving would-be shoppers with the perception (all-too-real in this case) that there’s ‘nowhere to park.’ Here’s how it went down in Providence.

This is a case where ITS may prove quite useful: Let the algorithms, not fallible human perception, guide the driver to the (properly priced) parking. In the meantime planners and politicians should take parking complaints with a healthy dose of salt.

Posted on Wednesday, January 20th, 2010 at 9:00 am by: Tom Vanderbilt
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Drive-Through Parking

In my drive-through piece a while back, I speculated the numbers about drive-throughs somehow being environmentally superior to parking lots might be off for a number of reasons, including the idea that some drivers use the drive through and then park. In any case, I came across this curious sign that seems to connote just that behavior, rather paradoxically.

Posted on Tuesday, January 12th, 2010 at 10:10 am by: Tom Vanderbilt
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Up at Yale

Calling New Haven-ites (New Havinians?): I will be appearing in a talk with the estimable Donald Shoup next week at Yale University.

Posted on Tuesday, January 12th, 2010 at 10:02 am by: Tom Vanderbilt
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On Gender and Parking

As I note in Traffic, there has been some research into parking and gender, ranging from the indefatigable John Trinkaus’ “informal looks” at “No Parking — Fire Zone” violations at a shopping mall (women driving SUVs were the leading offenders), to suggestions that female drivers spent more time searching for the “best” parking spot (to which the above cartoon alludes).

Now, Claudia C. Wolf and colleagues at Germany’s Ruhr University-Bochum have explored the idea of parking ability, in a new paper in Psychological Research titled “Sex differences in parking are affected by biological and social factors.”

As the authors note, some previous work has found men to have a slight edge on certain cognitive tasks involving spatiality, in particular the “Mental Rotation Test,” while women have, in some cases, outperformed men on more language oriented spheres, like the “phonological retrieval in the letter fluency task.” But real-world equivalents for things like mental rotation have not been in abundance. Which is why the authors headed to the parking lot.

During everyday life—and obviously especially during parking—individuals are required to imagine themselves from different perspectives, which involves mental rotation. A driver who steers towards a parking space must predict the outcome of spatial relationships between objects (including own car, parking space, further cars, and kerb) after changes in viewpoint, which arise from the car’ s—and thus the driver’ s motion.

But curiously, they note, “the cognitive mechanisms involved in parking have never been investigated.” Of course, it’s not just innate spatial ability that’s involved; confidence in one’s ability to do the task matters as well. This belief is “domain specific,” and can socially conditioned by stereotypes, etc.

For the test, the authors asked subjects, divided into similar levels of driving experience, to park an Audi A6 in various ways (back in, parallel, etc.) in a closed-off multi-story car park. The result? “The present data revealed a sex difference in parking performance in driving beginners as well as in more experienced drivers.” Women took longer to park the car, which might be seen as an offshoot of lesser risk-taking behavior by females in driving, but interestingly, even though men parked more quickly, they also parked more accurately, as measured by distance to neighboring cars.

Before we get into a whole “are men or women better drivers” argument, let’s remember that men also come out on top on another variable of driving performance: The tendency to get oneself killed or injured. And this was a relatively small sample. And it’s just parking, after all. And then there’s that question, raised by the authors themselves, of how much this is in any sense innate — always a dangerous word — and how much is generated by social expectations or other feedback loops along the way:

Additionally, unequal base levels of parking performance — which could be due to unequal spatial skills in unexperienced drivers — may have resulted in differential feedback during training of parking skills, leading to a change in self-assessment and thus differential behaviour and achievement… [I]n a recent driving simulator study, it was found that women, whose self-concept was manipulated by confronting them with the stereotype that females are poor drivers, were twice as likely to collide with pedestrians as women who were not reminded of this stereotype.

Strangely, just after reading this paper early yesterday, I came across an item in the BBC about new ‘car parks for women’ in China.

The women-only car park in Shijiazhuang city is also painted in pink and light purple to appeal to female tastes.

Official Wang Zheng told AFP news agency the car park was meant to cater to women’s “strong sense of colour and different sense of distance”.

The parking bays are one metre (3ft) wider than normal spaces, he said.

Were the Chinese government ministers reading Wolf, et al’s paper? And are they taking a potentially biologically innate, and perhaps marginal, difference, and whipping it up into an ever-perpetuating, and debilitating, social construct of drivers with particular, gendered needs? (not to mention the environmental impact of all that extra asphalt — three feet times the soon to be many, many millions of Chinese women drivers).

(thanks Peter)

Posted on Tuesday, December 29th, 2009 at 6:04 am by: Tom Vanderbilt
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Twenty’s Plenty

For those looking to explain why the U.K. has made comparatively greater advances in traffic safety than the U.S. over the last few decades, urban speed zones are one good place to look.

An article recently published in the British Medical Journal, “Effect of 20 mph traffic speed zones on road injuries in London, 1986-2006: controlled interrupted time series analysis,” by Chris Grundy, et al., notes that “the introduction of 20 mph zones was associated with a 41.9% (95% confidence interval 36.0% to 47.8%) reduction in road casualties, after adjustment for underlying time trends.”

The reduction, they also note, was greatest for young children — which brings up the point that it’s not merely children’s risk-taking behavior responsible for their deaths as pedestrians, that addressing driver’s behavior can make a difference — and mattered more for KIAs (killed or serious injuries) than for minor injuries. They also report that “there was no evidence of casualty migration to areas adjacent to 20 mph zones, where casualties also fell slightly by an average of 8.0% (4.4% to 11.5%).” Perhaps driving more slowly on one set of streets even had a carry-over effect. The reductions are impressive and seem beyond what might be explained by some other factor, such as a reduction in pedestrian volumes over that same time period (although other factors, like the presence of enforcement cameras, need to be kept in mind).

About now is where someone usually complains that putting up 20 mph signs is ineffective and won’t change driver behavior. But we’re not talking about mere signage here, we’re talking “self-enforcing roads,” with a variety of engineering and design measures, and as the authors write, some evidence “suggests that the self enforcing 20 mph zones are effective in reducing traffic speeds to an average of 17 mph, an average reduction of 9 mph.”

The benefit wasn’t merely for pedestrians. “A somewhat counterintuitive observation,” they write, “is the apparently large reduction in injuries to car occupants.”

And not surprisingly, given their findings, the authors argue for extending, where justified, the 20 mph zone throughout London, and other metropolitan regions. Which isn’t necessarily an easy task, as Shanthi Ameratunga notes in a reply, also worth reading. “Giving provincial or local agencies the authority to reduce national speed limits is an important step in achieving this vision. Yet the 2009 global survey on road safety reported that only 29% of 174 participating countries set speed limits of 50 km an hour or below on urban roads and allowed local authorities to reduce national speed limits. These findings probably reflect both the lack of evidence on cost effective speed management strategies in low income and middle income countries, and the reticence of most governments to enforce laws that limit driving speeds, possibly because of perceived public opposition.”

But progress is being made, at least in the U.K.

Posted on Tuesday, December 22nd, 2009 at 9:41 am by: Tom Vanderbilt
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Park Department

Some interesting parking-related figures I came across today, in a forthcoming paper in the journal Land Use Policy, “The environmental and economic costs of sprawling parking lots in the United States,” by Amélie Y. Davis, Bryan C. Pijanowski, Kimberly Robinson and Bernard Engel:

A large proportion, over 6.5%, of the urban footprint, is allocated to parking lots in Tippecanoe County, Indiana. We estimated that this is the same size as 1075 American football fields. In our mall study area, we found that parking lots exceeded the footprint of buildings they service by 20%.

There are many more spaces than registered vehicles (1.7×), households (6.3×) or people living in the county of driving age (2.2×). This implies that if all of the vehicles in the county were removed from garages, driveways, and all of the roads and residential streets and they were parked in parking lots at the same time, there would still be 83,000 unused spaces throughout the county. Annual ecological services value of these parking area represents over $22 M if they are all replaced by wetlands.

If the percentage of parking lot area in the county (0.44%) is scaled to the area occupied by the conterminous United States, the entire states of Connecticut, and Massachusetts (12,550 + 20,305 = 32,855 km2 ) would be paved over with parking lots.

Posted on Tuesday, December 15th, 2009 at 3:47 pm 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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Upcoming Talks

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

May 19, 2009
University of Minnesota Center for Transportation Studies
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June 23, 2009
Driving Assessment 2009
Big Sky, Montana

June 26, 2009
PRI World Congress
Rotterdam, The Netherlands

June 27, 2009
Day of Architecture
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Association of Transportation Safety Information Professionals (ATSIP)
Phoenix, AZ.

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Governors Highway Safety Association Annual Meeting
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California State University-San Bernardino, Leonard Transportation Center
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Yale University
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Delaware Center for Transportation

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Canadian Association of Road Safety Professionals
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Fondo de Prevención Vial
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Royal Automobile Club
Perth, Australia

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Wisconsin Department of Transportation’s
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Rutgers University
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Ontario Injury Prevention Resource Centre
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Idaho Public Driver Education Conference
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California Association of Cities
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American Association of Motor Vehicle Administrators
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Wednesday, October 26, 2011
Attitudes: Iniciativa Social de Audi
Madrid, Spain

April 16, 2012
Institute for Sensible Transport Seminar
Gardens Theatre, QUT
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April 17, 2012
Institute for Sensible Transport Seminar
Centennial Plaza, Sydney
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April 19, 2012
Institute for Sensible Transport Seminar
Melbourne Town Hall
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January 30, 2013
University of Minnesota City Engineers Association Meeting
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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
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Rochester, NY

August 18, 2013 “Ingenuity” Conference
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September 26, 2013
TransComm 2013
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Officials’ Subcommittee on Transportation
Grand Rapids MI



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