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Archive for the ‘Traffic Engineering’ Category

A Short History of Traffic Engineering

Via Copenhagenize.

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Posted on Tuesday, January 29th, 2013 at 6:34 pm by: Tom Vanderbilt
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Whatever Happened to Walking?

Starting today in Slate, I take a four-part look at walking, the “forgotten transportation mode,” in America and elsewhere.

Simply by going out for a walk, I had become a strange being, studied by engineers, inhabiting environments whose physical features are determined by a rulebook-enshrined average 3 foot-per-second walking speed, my rights codified by signs. (Why not just write: “Stop for People”?) On those same signs in Savannah were often attached additional signs, advising drivers not to give to panhandlers (and to call 911 if physically intimidated), subtly equating walking with being exposed to an urban menace—or perhaps being the menace. Having taken all this information in, we would gingerly step into the marked crosswalk, that declaration of rights in paint, and try to gauge whether approaching vehicles would yield. They typically did not. Even in one of America’s most “pedestrian-friendly” cities—a seemingly innocent phrase that itself suddenly seemed strange to me—one was always in danger of being relegated to a footnote.

Which is what walking in America has become: An act dwelling in the margins, an almost hidden narrative running beneath the main vehicular text. Indeed, the semantics of the term pedestrian would be a mere curiosity, but for one fact: America is a country that has forgotten how to walk. Witness, for example, the existence of “Everybody Walk!,” the “Campaign to Get America Walking” (one of a number of such initiatives). While its aims are entirely legitimate, its motives no doubt earnest, the idea that that we, this species that first hoisted itself into the world of bipedalism nearly 4 million years ago—for reasons that are still debated—should now need “walking tips,” have to make “walking plans” or use a “mobile app” to “discover” walking trails near us or build our “walking histories,” strikes me as a world-historical tragedy.

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Posted on Tuesday, April 10th, 2012 at 7:19 am by: Tom Vanderbilt
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Go Slow to Go Fast

My latest Slate column explores the concept of “rolling speed harmonization” on a Colorado highway.

As one report describes it, speed harmonization “holds that by encouraging speed compliance and reducing speed differential between vehicles, volume throughput can be maximized without a physical increase in roadway dimensions.”

The concept plays, in part, on one of traffic engineering’s core truths: Big speed differentials are dangerous. This is laid out in the “Green Book,” the bible of the American Association of Surface Highway Transportation Officials. “Crashes are not related as much to speed as to the range in speeds from the highest to lowest,” the book states. “Studies show that, regardless of the average speed on the highway, the more a vehicle deviates from the average speed, the greater its chances of becoming involved in a crash.”

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Posted on Sunday, October 16th, 2011 at 6:49 am by: Tom Vanderbilt
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Carmaggedon

I joined the stable again over at the New York Times’ Room for Debate, this time on the idea of full highway shutdowns.

Just for historical curiosity, here’s my original, somewhat more fanciful (but contextual) submission:

It’s perhaps appropriate that the town that produced Michael Bay should summon such a bombastic bout of overblown apocalyptic fury as the forthcoming “carmaggedon.” Given the life-support functions of the 405 in the L.A. region’s transportation monoculture, perhaps the hype is warranted, but the truth is, highways are closed all the time, and there’s been much study and practice into how to do it most effectively.

The perturbed driver may be asking, ‘why do they have to close the whole thing down? Why can’t they just do it a lane at a time?’ And indeed, any number of strategies have been tried to mitigate traffic impacts during construction, from nocturnal work crews (which has been found to add 6% to the base price of a project) to various incentive plans for road contractors.

But as research by the Federal Highway Administration has shown, closing down a highway entirely means the job gets done, on average, 63 to 95 percent faster than projects that tried to maintain a semblance of traditional traffic. Why? No traffic means no interference from drivers, no work-zone crashes (in 2007, for example, 835 people were killed in work zone crashes) or other bad behavior, not to mention that the trucks hauling materials and workers don’t have to sit in the same congestion as everyone else as they go back and forth.

The secret to making this happen, as is happening in Los Angeles, is to enact a comprehensive “Traffic Management Plan,” with careful study of alternate routes and “network effects.” Implicit in this is to issue a prediction of Nostradamusian direness; to do for weekend driving what Jaws did for ocean swimming (“just when you thought it was safe to go to Santa Monica”).

This reason this generally works is that in any road system, there is a certain amount of elasticity; not every driver on that road has to be there at that time. There may be another route, another mode of travel. Or they just stay home. When highway segments are taken out because of disaster (as in the Minneapolis I-35 W bridge collapse, or the collapse of Manhattan’s West Side Highway) the surrounding roads do not automatically filled up with all the diverted drivers; rather, some traffic “disappears.” To quote two of the main findings of a report analyzing any number of road closures, planned or otherwise, by transport researcher Phil Goodwin and colleagues: “When roadspace for cars is reallocated, traffic problems are usually far less serious than predicted” and “Traffic reduction is partly explained by recognizing that people react to a change in road conditions in much more complex ways than has traditionally been assumed in traffic models.”

When Los Angeles partially closed the 710 expressway for eight weekends, it was able to reduce traffic by 37%. Interestingly, though, traffic was lowest through the work zones the first weekend, and then grew gradually on each successive weekend, as L.A. drivers, in a kind of city-wide learning curve, began testing the drive. In the case of the 405 closure, of course, drivers won’t have that option. There’s no knowing how bad or how good it’s going to be, until you’re in it.

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Posted on Friday, July 8th, 2011 at 6:46 am by: Tom Vanderbilt
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NYT Room for Debate

On the off chance you missed, me and some other fuzzy headed Jane Jacobs types, a tenured suburbanite urbanist or two, as well as a few random tar-breathing asphalt heads, discuss, in the paper of record, the idea of bringing some European-style traffic demand management to U.S. shores. The pyrotechnics are to be found here.

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Posted on Thursday, June 30th, 2011 at 1:10 pm by: Tom Vanderbilt
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3-Way Street

3-Way Street from ronconcocacola on Vimeo.

Via http://blog.ronconcocacola.com/

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Posted on Monday, June 6th, 2011 at 8:58 am by: Tom Vanderbilt
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Use Both Lanes

As discussed in Traffic, sometimes the best way to eliminate tension over ‘late merging’ is to simply eliminate the concept, as the Illinois DOT seems about to do.

“Once people get used to it, it seems to work well,” Wegmeyer said. “As long as traffic alternates at the merger, it should go more smoothly.”

Of course, that “as long as” still presents challenges, as those people in the “open lane” may still feel some sense of priority over those they view as late-arriving interlopers.

(thanks Darrin)

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Posted on Tuesday, May 24th, 2011 at 12:43 pm by: Tom Vanderbilt
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A Response to Hainline, Steisel, and Weinshall

I am glad that my posting on the Prospect Park West bike lanes occasioned a serious and thoughtful response (see the comments).

I wanted to reply to a few points.

They write:

(1) PPW is not simply an arterial roadway between intersecting streets (as is the adjacent roadway inside Prospect Park, which, we have argued, would be a more appropriate location for a two-way bike lane). Rather, PPW borders high-density residential blocks—with a school and elder-care facility (on one side of the street) and entrances to Prospect Park (on the other). This means that on a less-than-one-mile stretch of roadway, thousands of residents and park-goers are continuously entering or exiting school buses, wheel-chair vans, taxis, or driveways, while dozens of Fresh Direct, UPS, Fedex, USPS trucks, moving vans, and other delivery vehicles are also blocking one of the two remaining traffic lanes. This requires that drivers in the blocked lane continuously shift into a single more-heavily-used traffic lane to avoid the blockage. And since this single lane is now narrower on a significant stretch of PPW, if not the entire street (as our measurements, pace Vanderbilt’s assertion to the contrary, clearly show), there is less margin to avoid car doors opening, drivers or passengers squeezing into their vehicles, parents lifting babies from their car-seats, cars edging into or out of parking spots, or side view mirrors extending from vehicles. These circumstances, rather than producing a “calming feeling,” are more likely to produce irritated impatience, at best.

I admit that the studies I referred to are for road types different from PPW; in part this is a necessity because of the rather unique nature of PPW itself. But I am interested here in their description of all the exiting school buses, UPS trucks, parents getting babies out of cars, Fresh Direct vans, etc. Given this huge amount of stopped traffic, and pedestrian activity, to my mind the most important safety benefit we could bring to those users is a reduction of the speeds on that street — which were typically well above the speed limit prior to the installation of the bike lane. Speed, and the violating of right of way — not lane changing and merging — is the root cause of the vast majority of serious traffic injury in New York City. As I’ve said repeatedly, drivers, in their ‘irritated impatience,’ have tended to use PPW as a high speed arterial to neighborhoods beyond Park Slope rather than the neighborhood street it should be. I will take an infinite number of bent mirrors over the lives or health of any one person.

In their second point, they note:

“In addition to the option of moving the lane onto the adjacent roadway inside the park, making the PPW bike-lane one-way is the other proposal we have made as members of “Neighbors for Better Bike Lanes.”

I would take a one-way bike lane over no bike lane; but as a condition of that one-way status, I would call for a protected one-way bike lane, in the other direction, on Eighth Avenue, which suffers from some of the same speed problems as PPW.

They then note:

(1) Vanderbilt’s basic argument relies on the perception of increased safety that roadway users (drivers, bikers, and pedestrians) may have when more drivers and riders are using fewer and narrower lanes, because their awareness of other roadway users is heightened. But this perception of increased safety is not what users of PPW have experienced. In a self-selected survey of over 3,000 Brooklynites conducted by Councilmembers Lander and Levin, most people—bikers were the only exception—reported feeling less safe after the bike lane was installed (Ref. 2).

This misrepresents what I have said, and indeed highlights a problem: Perception of safety and actual safety in traffic are not always the same. When subjects have been asked to identify what they think are crash hot spots in certain locations, for example, they often choose places with low numbers of crashes, not the actual hot spots. When roundabouts are installed, it’s quite common for the local populace to protest that their safety has been compromised — when in fact, roundabouts, as have been documented in any number of studies, tend to make things safer for all road users. ‘Shared space’ experiments in Europe and the U.K. have shown a similar disconnect between perceived and actual safety.

But let’s stick to what we know: The actual numbers from PPW, which are now available, via the Brooklyn Paper:

“Crashes are down from an average of 30 in six months to 25, or 16 percent.

• Crashes that cause injuries are down from 5.3 in six months to two, a whopping 63-percent drop.

• Before the project, a crash was twice as likely to include an injury.

• Injuries to all street users dropped 21 percent.

The data also found that since the lane was installed last June, there have been no reported pedestrian injuries and no pedestrian or cyclist injuries from pedestrian-bike crashes.”

Granted, crashes involving pedestrians and bicycles tend to be underreported, but vehicle crashes, particularly involving injury, are not — and by this measure, the addition of the lanes has actually made for a safer environment for all road users. An increase in active transportation; a decrease in injury — I fail to see this as a problem.

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Posted on Thursday, January 20th, 2011 at 10:33 am by: Tom Vanderbilt
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Painted Roundabout

From somewhere in Germany, I believe (would be curious to know the exact location), a roundabout with nothing in the center save paint. I’d be curious about the stats for this intersection; on the whole it seems more or less orderly (there’s confusion but low-speed confusion), but some people just seem to blow straight through as if they had a green light in a signalized intersection.

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Posted on Saturday, January 15th, 2011 at 1:49 pm by: Tom Vanderbilt
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Desire Named Streetcar

My latest Slate column looks at two transportation forms, the monorail and the streetcar, each with their supporters and each with their detractors, and how time’s arrow seems to have inverted somewhere along the way:

What’s interesting about Disney World and Disneyland is not merely the range of transportation options, but the mixture of new and old modes they represent. These varied ways to get around reflect biographer Neal Gabler’s observation that Walt Disney was “at once a nostalgist and a futurist, a conservative and visionary.” One imagines he would have been equally happy riding the retro trolley on Main Street as whisking through Tomorrowland in an ultramodern monorail.

But there is something else to note here. The monorail—which must have looked to Disney and the world like the transportation of the future in the 1950s—is now, to many, considered a historical footnote, a relic of World Expos or, at best, an automated ride between airport terminals. America’s highest-profile monorail project, the expansion of Seattle’s line, was plagued by cost overruns and funding gaps, and was finally dissolved in 2005 (costing taxpayers $125 million). The Las Vegas monorail has filed for bankruptcy. At the same time, those retro streetcars, which Disney himself rode in Kansas City in the early 20th century and which must have seemed to him part of a vanishing past, are returning (or may soon return) to any number of American cities, including Washington, D.C.; Cincinnati’ Tucson; Atlanta; Dallas; St. Louis; and Salt Lake City.

So the future we thought we were going to get somehow seems antiquated, while the past looks increasingly, well, futuristic. Why is the trolley ascendant as the monorail declines?

[P.S. I do realize a fair number of people prefer buses to either of these options, but for space it was cut. An original line read: "Light-rail supporters — and transportation people, whether for reasons of funding, fandom, or something else, and even if they’re working toward similar goals, tend to cleave into camps (a third group, the bus people, find their vessel of choice superior to both the light-rail and monorails) — counter with a battery of well-practiced rejoinders..."]

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Posted on Wednesday, January 12th, 2011 at 5:40 pm by: Tom Vanderbilt
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On Bike Lanes, Road Widths, and Traffic Safety

There was an assertion made in one of the letters (signed by Louise Hainline, Norman Steisel, and Iris Weinshall in response to a recent New York Times editorial on cycling that caught my eye:

When new bike lanes force the same volume of cars and trucks into fewer and narrower traffic lanes, the potential for accidents between cars, trucks and pedestrians goes up rather than down. At Prospect Park West in Brooklyn, for instance, where a two-way bike lane was put in last summer, our eyewitness reports show collisions of one sort or another to be on pace to be triple the former annual rates.

The first point is that while the PPW conversion did take away one travel lane, the width of the existing lanes was not altered. So there may be fewer lanes, but they are not, as the letter argues, “narrower.” It may be that entire street feels narrower, which, as an emerging school of what I’ll call ‘behavioral traffic calming’ argues, is actually a good thing. Drivers, as I’ve quoted Ezra Hauer as saying, “adapt to the road they see.” They either do not see traffic signs or fail to read their meaning correctly. If they see a wide open, long boulevard, they will drive like this.

Even if the lanes were narrowed, as John LaPlante recently argued in the journal of the Institute for Transportation Engineers, “there is no significant crash difference between 10-, 11-, and 12-foot lanes on urban arterials where the speed limit is 45 mph (or less).” (a finding, he notes, that was unfortunately left out of AASHTO’s recent Highway Safety Manual).

And there’s something deeply suspicious about that “eyewitness reports” note; were they actually out there, day after day, meticulously logging conflicts and crashes (tellingly, they make no note of severity)? And why, if everything was so great with the street before, were they even doing these “before” counts? As the case of roundabouts shows, what people perceive as individual danger often does not translate at all to an increase in overall risk; in fact, it’s quite the opposite.

But let’s take that notion — that fewer and narrower lanes lead to more crashes. This is a staple of traffic engineering, and in fact it does have some validity — when applied to highway environments (which PPW at times unintentionally resembles). Even here, though, the effects are often not ‘statistically significant’ and ‘more complex than expected.’

But in non-highway environments, there’s all kind of evidence that reducing the number of lanes (a.k.a. the ‘road diet’) can have positive safety benefits. As the Federal Highway Administration has noted:

Road­ diets­ can­ offer­ benefits ­to­ both ­drivers ­and­ pedestrians… road diets may reduce vehicles speeds and vehicle interactions, which could potentially reduce the number and severity of vehicle-to-vehicle crashes. Road diets can also help pedestrians by creating fewer lanes of traffic to cross and by reducing vehicle speeds. A 2001 study found a reduction in pedestrian crashing risk when crossing two-and three-lane roads compared to roads with four or more lanes.

But what if one of those lanes your crossing is a bike lane? Surely that must make things less safe, no? More interactions in less space. In a forthcoming paper to be published in the Journal of Environmental Practice Norman Garrick and Wesley Marshall examined 24 California cities (12 with relatively low traffic fatality rates, 12 with relatively high rates). They found that the cities that had a higher bicycle usage had a better safety rate, not just for cyclists but all road users. They write:

Our results consistently show that, in terms of street network design, high intersection density appears to be related to much lower crash severities. Our street design data also contains strong indications of these trends; for example, the high biking cities tend to have more bike lanes, fewer traffic lanes, and more on-street parking. At the same time, large numbers of bicycle users might also help shift the overall dynamics of the street environment – perhaps by lowering vehicle speeds but also by increasing driver awareness – toward a safer and more sustainable transportation system for all road users.

And as Eric Dumbaugh, of the University of Texas A&M, notes, “most recent research reports that wider lanes on urban streets have little or no safety benefit, at least to the extent that safety is measured in terms of empirical observations of crash incidence” (e.g., Potts, I.B., Harwood, D.F., & Richard, K.R. (2007). Relationship of Lane Width to Safety for Urban and Suburban Arterials. Transportation Research Board 2007 Annual Meeting; Milton, J., & Mannering, F. (1998). The relationship among highway geometries, traffic-related elements and motor-vehicle accident frequencies. Transportation 25, 395–413; and so on).

But the authors of this letter are not trafficking in empirical evidence, even as they allege that the NYC DOT’s data “more puzzlement than enlightenment.” It’s unfortunate that this letter is signed by a former DOT commissioner, and an academic — who should both know that it is evidence and analysis, not vague “eyewitness” reports and random testimony, upon which good science, planning, and safety interventions are made.

And as always, curious to hear of more work either supporting or countering what I’ve said here.

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Posted on Thursday, December 23rd, 2010 at 12:47 pm by: Tom Vanderbilt
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The Car As Renter of the City, Not Landlord

I have a short piece in the current World Policy Journal in response to the question of the future of the city. In this telegraphic dispatch I addressed the place of the car in the city (N.B.: The piece could also be headlined: ‘An Open Letter to Marty Markowitz’):

We spent much of the twentieth century engaged in a campaign to retrofit our cities to the car. However much this may have seemed to make sense at the time, it now looks more like a misdirected effort to save the city by destroying it. As plentiful as the benefits of individual vehicular mobility may be, the large metropolis can never comfortably accommodate any more than a fraction of its citizens in this manner, and we have learned the consequences of trying to do so. Ever-lengthening commutes have meant degraded public spaces, negative health outcomes, social fragmentation, infrastructure whose maintenance goes underfunded.

In the city of the future, we need to pursue policies that allow for safe, efficient and affordable transport of the many, while recognizing that market-based approaches that so rationally apportion space in the private sector can and should be applied to the valuable urban space — in the form of roads and parking spaces—that cities essentially give away. We need to recognize that streets are public spaces too, and not merely, in the old view of 1930s utopian modernism, channels for moving as many vehicles as quickly as possible. The car will continue to exist, but should be treated as a “renter” of the city, not its landlord. The urban car of the future should be shared, smaller, and slower.

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Posted on Tuesday, December 14th, 2010 at 2:30 pm by: Tom Vanderbilt
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Why Traffic Slows at Tunnel Approaches

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


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

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

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

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

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

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Posted on Wednesday, November 10th, 2010 at 11:40 am by: Tom Vanderbilt
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On the Origins of the Jersey Jughandle

It took me a long time to, er, come around to the logic and efficacy (at least in safety terms) of the Jersey Jughandle, but following a prompt from Anthony Townsend, do any NJ DOT readers or likewise know how the Garden State came to be the leader in this somewhat rare infrastructural form? Taking a stab I’d say it had something to do with the state’s density and preponderance of highways, but can anyone elucidate us beyond that; e.g., the name of the inventor, etc.

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Posted on Wednesday, October 27th, 2010 at 6:27 am by: Tom Vanderbilt
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End of the Road for Dutch Per-Kilometer Pricing

No time to comment on this as, coincidentally, I’m about to leave for the Netherlands, but Bern Grush sifts through the ashes.

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Posted on Wednesday, October 6th, 2010 at 12:27 pm by: Tom Vanderbilt
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Figure 8 Roundabout in Buffalo

A colleague sends the above photo of a “double roundabout,” in Buffalo, NY (or it’s suburbs). While your first thought might be, wow, how confusing, consider the Google Map image below that shows the original intersection — too big, actually two intersections masquerading as one (one can imagine cars getting “trapped” in that little extra segment, and box-blocking problems). Undoubtedly there was a crash problem, hence the double roundabout. Which are used in the U.K. (and taken to its logical extension in the “Magic Roundabout”, of course, but are, as far as I know, relatively novel here. Anyone live near here by chance and care to weigh in?

(thanks Nate)

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Posted on Thursday, September 9th, 2010 at 7:47 am by: Tom Vanderbilt
14 Comments. Click here to leave a comment.

Desire Path Crosswalk

An interesting prototype design via the PFSK Conference for an “ergonomic” crosswalk that takes into account pedestrians’ natural inclinations to want to shorten the distance it takes them to cross the street (as someone once told me, ‘pedestrians are natural Pythagoreans’). I can foresee a problem with cars, who already stray into the crosswalk, having a bit of a problem lining up. And while I like the red/yellow LED light concept in theory, does it just lessen our tendency to look at the actual environment for safety cues?

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Posted on Wednesday, September 8th, 2010 at 12:04 pm by: Tom Vanderbilt
6 Comments. Click here to leave a comment.

The Shady Side of Transportation

Over at KCRW’s Design and Architecture, Francis Anderton considers a part of the built environment often overlooked in transportation questions: Shade. It is remarked that trees in Los Angeles are placed to provide shade for cars, not people walking on sidewalks.

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Posted on Tuesday, July 6th, 2010 at 7:34 am by: Tom Vanderbilt
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China, India, and the Road Death-GDP Correlation

The New York Times notes:

India overtook China to top the world in road fatalities in 2006 and has continued to pull steadily ahead, despite a heavily agrarian population, fewer people than China and far fewer cars than many Western countries.

It goes on to cite a few reasons:

A lethal brew of poor road planning, inadequate law enforcement, a surge in trucks and cars, and a flood of untrained drivers have made India the world’s road death capital. As the country’s fast-growing economy and huge population raise its importance on the world stage, the rising toll is a reminder that the government still struggles to keep its more than a billion people safe.

In China, by contrast, which has undergone an auto boom of its own, official figures for road deaths have been falling for much of the past decade, to 73,500 in 2008, as new highways segregate cars from pedestrians, tractors and other slow-moving traffic, and the government cracks down on drunken driving and other violations.

As R.J. Smeed first noted, having fewer cars is by no means an indicator that one will have fewer traffic fatalities (and an important distinction in the developing world is that traffic fatality categories are topped by pedestrian deaths). But one thing that goes unmentioned in the piece is research, cited in Traffic, by Elizabeth Kopits and Maureen Cropper, that links a nation’s rate of traffic fatalities to its GDP. When GDP climbed from $1200 to $4400 in the countries studied, the fatality rate dropped by a factor of three.

According to the CIA Factbook, the 2009 estimated GDP of China was $6600, while in India it was $3100. Just by this measure alone, the discrepancy between the two countries could be predicted, if not fully explained (for there would be many other factors at play here, like culture, governmental structure, etc.). It’s not hard to imagine why higher GDP would lead to fewer deaths (in this regard it’s not properly correct to call traffic deaths, as is often done, a “disease of affluence”); as development levels increase, there’s not only more money for engineering, enforcement, etc., but also a reduced likelihood of corruption (roads are built to standards, police less willing to take bribes), accompanied by a greater societal emphasis in safety in all kinds of areas of life. But the real question is how India can close the huge fatality gap with China even if it can’t immediately narrow the GDP gap.

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Posted on Wednesday, June 9th, 2010 at 7:52 am by: Tom Vanderbilt
3 Comments. Click here to leave a comment.

Speed Nudge

A Spanish company, Badennova, has developed what it calls an “intelligent speed bump,” which only acts as a speed bump if you’re going faster than the posted speed:

When vehicles traveling at the appropriate speed pass over the top, the intelligent speed bump provides no resistance and, as a consequence, does not cause any damage. For cars moving at excessive speed, however, the speed bump hardens and therefore provides the same resistance as any standard speed bump.

This behaviour is due to a non-Newtonian fluid which constitutes the filling material of the intelligent speed bump. These kinds of fluids behave differently than water. This means that their flow properties cannot be described by a single constant value of viscosity. There are different types of non-Newtonian fluids. The intelligent speed bump contains a so-called shear-thickening fluid (also known as dilatants).
Dilatants are suspensions whose viscosity increases with the rate of shear, i.e., the strain rate raises with the rate of shear. The dilation effect occurs when closely packed particles are combined with enough liquid to fill the gaps between them. At low velocities, the liquid acts as a lubricant, so the non-Newtonian liquid flows easily. At higher velocities, the liquid is unable to fill the gaps created between particles, and friction greatly increases, causing an increase in viscosity.

As a consequence, the non-Newtonian material allows the speed bump to change from a soft to a solid state according to the vehicle’s speed.

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Posted on Wednesday, June 9th, 2010 at 7:15 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 Slate.com Transport column to me at: info@howwedrive.com.

For publicity inquiries, please contact Kate Runde at Vintage: krunde@randomhouse.com.

For editorial inquiries, please contact Zoe Pagnamenta at The Zoe Pagnamenta Agency: zoe@zpagency.com.

For speaking engagement inquiries, please contact
Kim Thornton at the Random House Speakers Bureau: rhspeakers@randomhouse.com.

Order Traffic from:

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

[del.icio.us] [Digg] [Facebook] [Google] [MySpace] [Slashdot] [StumbleUpon] [Yahoo!]
U.S. Paperback UK Paperback
Traffic UK
Drive-on-the-left types can order the book from Amazon.co.uk.

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
Toronto

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
BoingBoing.com “Ingenuity” Conference
San Francisco, CA

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

 

 

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