Archive for the ‘Traffic Engineering’ Category

Roads That Kill, Drivers Who Kill

A few kind readers have sent along an op-ed in the Boston Globe, which the website sums up thusly:

“Traffic injuries kill more than a million people a year worldwide, including 40,000 a year in the United States. Yet when a fatality occurs few people blame the roadway for the death.”

The piece makes some good, worthy points (and it’s important to remember that the concept of safer road design can also entail — gasp — forcing drivers to slow). It’s a bit like the concept of “fire-safe cigarettes.” We can try to educate people not to smoke in bed, we can fine them if they do; or we can build a device that extinguishes itself, lowering the potential for a human mistake.

But it also reminded me of a story in today’s New York Times about the deadly crash on the Taconic Parkway (in which the driver was subsequently reported to have a BAC twice the legal limit; before this, there was a grasping search to blame improper road design or poor signage). The story tries to insinuate that the parkway, designed in the 1920s, is no longer safe — the reason, of course, having less to do with the road itself than that drivers no longer feel compelled to drive the 55 mph speed limit (partially because it became a conduit for a sprawl-based commuter-shed). Curiously, though, the piece notes that the Taconic turns out to be safer than comparison roads, thereby somewhat deflating the sense of urgency that this is a road in need of serious examination.

And yet, after the crash, officials put up additional “wrong way” signs at the particular intersection where the driver joined the highway. A natural response, perhaps, but one done more out of reflex (the “accident black spot” approach) than thought: What about all the other entrances? Given that the driver drove for several minutes, clearly against the flow of traffic, what would another ‘wrong way’ sign have done? The point here is that road engineering can only get us so far in reducing deaths; driver behavior matters.

Posted on Tuesday, August 18th, 2009 at 2:05 pm by: Tom Vanderbilt
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Emotionally Intelligent Bollards

One of the most universal, and seemingly intractable, problems in the world of traffic is controlling drivers’ speeds on local streets, particularly those with children present. The latest approach, in Leicester, England, combines hardcore traffic engineering — steel bollards — with a more humanistic side: They literally look like small children standing on the side of the road.

There is, admittedly, a bit of a Village of the Damned look to the bollards — and yet also something rather cheerful, something like foosball players — but perhaps, echoing Daniel Pink’s “emotionally intelligent signage” proposal, they may trigger some instinctual response, reminding drivers of the presence of humans (and, after all, studies have shown that images of humans, particularly human eyes, can be as persuasive as real humans).

Not surprisingly, the locals are a bit divided.

Sylvia Thomas, who lives in nearby Greenhill Road, said: “I can’t see the point of them. If they are there to calm traffic they don’t work, because one has already been knocked over.

“They are quite strange.”

Helen Evans, 44, from Knighton, said: “They look great. I think they’re cute – and hopefully they will make people drive more carefully and remember there are children around here.”

As to the first commenter, rather than viewing it a failed solution, the idea that one has already been knocked down might simply demonstrate the extent of the problem. And the bollards are merely one part of a wider strategy, including striping and a new 20 mph speed limit.

From another story came this comment:

The RAC told Sky News Online that there was a risk “the statues will become a distraction with drivers focusing on them rather than the road ahead.”

One way to deal with that issue would be to put a few in the road. But of course there’s also the issue that real pedestrians will become a distraction — do we ban them from roadsides? Do we strip any sign of life from city streets so drivers will not have their precious roads obscured, their perilous attention (probably already compromised by their phone) fractured any further?

In any case, I’ll be curious to hear of any before/after speed comparisons.

Posted on Sunday, August 16th, 2009 at 10:21 am by: Tom Vanderbilt
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The Leftist Insurgency in Samoa

I’ve got a new piece up at that considers that ever vexing question: Which side of the road should we drive on? And should we all do it the same way?

Here’s the opener:

A revolution is afoot in the small Pacific island nation of Samoa. Mass demonstrations, the biggest the country has ever seen, have rocked the capital. A new political party has formed in an attempt to depose the prime minister. The airwaves crackle with dissent.

As is often the case in political strife, a left-right divide underpins the Samoan turmoil. In this case, left vs. right refers to which side of the road Samoans are meant to drive on. At 6 a.m. on Sept. 7, Samoans, who for over a century have navigated on the right — like their neighbors in American Samoa — will change over to the left.

Posted on Friday, August 14th, 2009 at 9:55 am by: Tom Vanderbilt
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No Phones In School Zones

I’m currently in Texas, and just heard an item on the radio about a curious new law: That it’s illegal to use a (hand-held) cell phone in a “school zone.”

And, as an article by Ben Wear (who was on my panel back at the Texas Book Festival last year) in the Statesman notes, cities like Austin now have to (or don’t, it’s still a bit up in the air) post signs alerting drivers to the presence of this law, otherwise police cannot enforce.

Robert Spillar, the City of Austin’s transportation director, said the city has not set aside money for the signs. Nonetheless, it will begin installing them this fall, starting with elementary schools. It could take two years to get them all up, he said.

“I don’t see how we can not put them up,” Spillar said. He said he isn’t sure the mere presence of signs will change driver behavior, and said some sort of education program might be necessary to get the message across. “It’s an unfunded mandate that has our backs against the wall. We can’t enforce it if the signs aren’t up.”

This is the first I’d heard of such a particular distinction being made in a particular zone, and I’m having trouble seeing the reasoning, or the safety impact. The first thought that jumps to mind is that a driver on a cell-phone is hardly likely to pick out a “no cell-phone” sign, much less expeditiously hang up their call as they approach. The second is that signs warning of “school zones” themselves, while a bit better — particularly when backed up flashing lights — than the ubiquitous (and absolutely ineffectual) “Slow Children” signs that are not officially recognized by engineers, tend to be little regarded as well, at least based on various tests in which drivers were still found to be routinely exceeding the speed limit; typically it’s the parent bringing their kids to the very same school. The entire concept of “School Zones” is a bit wanting, really, prone to driver and legal confusion, not to mention that it raises that eternal question: One is supposed to drive slowly and attentively on this stretch past a school, but it’s then OK to accelerate to higher speed a block later (a block on which there may be just as many children)?

And then, on the cell phone issue, we’re again making odd distinctions: We’re admitting that cell phones are a hazard to use when driving around groups of children at schools, but somehow OK when driving among groups of pedestrians or cyclists or children on the blocks in front of their homes — or in fact every other car on the road? And that it’s OK for drivers to zip past schools while talking on their hands-free-not-brain-free unit?

And then there’s the aesthetic blight of all the extra signage — more signs for drivers to ignore — not to mention all the money going to put the signs up, just so a law can be enforced; it seems rather ridiculous that if a state law is passed declaring it illegal to use cell phones in a school zone, one would have to expensively repeat that statement at every already marked school zone. After all, we don’t feel the need to erect signs announcing that driving while impaired is illegal, in school zones or anywhere else.

As always, any experiences or technical clarifications welcome.

Posted on Wednesday, August 12th, 2009 at 5:14 pm by: Tom Vanderbilt
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Does Your City Make Its Roads Look Big?

Former NJ-DOT-er Gary Toth (now with the project for Public Spaces) recently visited the Netherlands, a country that not so long ago had a worse traffic safety record than the U.S., but which now has a far superior one. There are a number of explanations, but in an interesting post (which echoes some material in Traffic), he singles out differing national approaches to the “forgiving road” concept:

Forgiving Highways is a concept that designs roads to “forgive” mistakes made on the road. It seeks to smoothly redirect the vehicles that leave roads, and allow wide enough clear zones to bring vehicles to controlled stops if and when they leave the roads. Breakaway supports, burying the end of guardrail, clearing the roadside of unneeded obstacles, and flattening and rounding slopes and ditch sections became standard design as part of the concept.

The idea that Forgiving Highways (wider and straighter) would reduce crashes on non-freeways took root during the 1966 National Highway Safety hearings. Leading the way was a nationally revered expert on safety: Kenneth Stonex, who during his career at General Motors, oversaw much of the research that created the basis for the Interstate Highway safety standards. Justifiably marveling in the remarkable safety record of the Interstates, Stonex and others sought to apply the Interstate principles to the rest of our roads. “What we must do is to operate the 90% or more of our surface streets just as we do our freeways… [converting] the surface highway and street network to freeway road and roadside conditions,” Stonex testified. It sounded logical at the time… and a great political solution, because the responsibility for fixing the problem once again fell on government, not the individual. We dove deep into the Forgiving Highway philosophy and still have not come up for air.

The Dutch also believed in technology and Forgiving Highways. However, they began to notice that while this worked on the high speed freeways and the low speed residential areas, they still had a problem in their “built up” areas. Recognizing that it is in these areas that they have the biggest conflicts between the purpose of roads for moving people and the value of roads in providing for exchange and access, they began to commit themselves to a different approach. They began designing roads in built up areas that induced motorists to operate their vehicles in ways and at speeds that were appropriate for passage through urbanized areas. The Dutch came to understand that the post-World War II world wide approach to making roads wider, straighter and faster simply doesn’t work on local and commercial roads in urbanized areas.

In the US, application of the Forgiving Highways approach in urban areas did accomplish its mission when vehicles did leave the road. However, as an unintended consequence, vehicular speeds go up. Drivers responded to their environment. Put them on a stretch of road that is wider, flatter, and straighter and they drove faster. While okay on controlled access freeways where there are no adjacent land uses or pedestrians, and where sight distances are near infinite, curves are flat and opposing roadways are separated by wide medians or center barriers, higher speeds caused problems in built up areas. Yet we were so caught up in the paradigm that we never stopped to check to see if we were getting the desired result.

Posted on Wednesday, August 12th, 2009 at 7:19 am by: Tom Vanderbilt
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Silent Majority on Red-Light Cameras?

Via online only Seattle comes an interesting tale of tentative success with red-light cameras.

This bit stood out:

A random telephone survey of 400 people last August showed an 85 percent approval rate, Quinn said. And city officials continue to get unsolicited recommendations for intersections to install new cameras.

I don’t know the specifics of that survey, but given that nary a day goes by that I don’t hear the old charges about cameras “increasing accidents” — without identifying the much more serious crashes that same cameras have reduced — and being simple revenue-raising tools for municipalities, I was surprised by the high level of seeming support.

Or maybe it’s a Seattle thing (I once received a jaywalking warning there by an officer in blue).

Posted on Tuesday, August 11th, 2009 at 5:48 pm by: Tom Vanderbilt
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Stop Making Sense

I was delighted to come across this bit on the blog Alternatives to Valium, as the writer visits with the former lead singer of the Talking Heads (and transportation writer) David Byrne:

And this, really, is the essence of David Byrne. He could, we may assume, afford to take a taxi, but, armed with his free maps from the London Cycle Campaign, he chooses to bike it, even when his journey involves an encounter with the Elephant and Castle roundabout. “Oh my God! Yes. I’ve heard that roundabouts are good for traffic, better than stoplights. Some guy [Tom Vanderbilt] has a book out called Traffic; there was a study, and there are fewer accidents on roundabouts than traffic lights because on roundabouts, it’s so precarious, you have to really be aware, and stop texting on your cellphone. Whereas with stoplights, people feel like the light does the job for them. So they’ll pull out when it turns green, and not think that someone else may have missed the light.”

The ‘some guy,’ to me, was rather perfect; it’s cooler in a way than actually being name-checked because a.) this shows that David Byrne doesn’t actually know me, and this isn’t just log-rolling and b.) the ideas are preceding me, which is the way it should be. I wouldn’t necessarily say that this really captures my feelings on roundabouts 100%, but it’s good enough.

After I wrote the roundabouts piece recently in Slate, there was a lot of chatter about pedestrian safety, and how some people don’t feel comfortable crossing at roundabout intersections. One thing to keep in mind, however, is that roundabouts can be as safe, if not safer, for pedestrians than conventional intersections for some of the same reasons they are for drivers. And one reason that might not have been considered is how they use space. To wit, the photos below, which come from Asheville, North Carolina, which has converted a number of downtown intersections, like those pictured on College Street, to roundabouts.

Here’s the before:

And here’s the after (not the most current ‘after,’ mind you, and not the very same location, but you get the general drift):

One thing that roundabouts do away with is the need for a dedicated left-turn lane. Left-turn lanes — there are generally two — have the consequence of making intersections wider. If there’s one iron law of pedestrian safety, it’s that the more lanes you have to cross, the less safe it is (for a number of reasons). Instead of things like left-turn lanes, you can fill the space with planted medians, which are not only more aesthetically pleasing, making the downtown seem more like a downtown than a stretch of asphalt, but provide safer crossings for pedestrians. Looking at the two images above, it’s instantly clear which one you’d rather walk across, traffic lights or not (and incidentally, there have been no pedestrian crashes at these intersections since 2005, the city’s head traffic engineer informs me).

Posted on Monday, August 10th, 2009 at 3:16 pm by: Tom Vanderbilt
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The Merge Wars, Revisited

From New Jersey, the state that give birth to Traffic, comes this appraisal of late and early merging (yes, I’m quoted), bound to be a issue this year as stimulus spending drops a torrent of orange cones across the Garden State.

Posted on Friday, August 7th, 2009 at 9:54 am by: Tom Vanderbilt
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Nonsensical Friday Posting

Vis a vis the hottest, most annoyingly ear-worming song of the summer, referenced in the above video, I wonder how Trip Generation (and ditto Parking Generation) handles combination Pizza Hut/Taco Bells? Do they generate more, fewer, or the same amount of trips as individual Pizza Huts and Taco Bells? And is that a more potent combination than the combination Dunkin’ Donuts/Subway/Baskin Robbins?

Posted on Friday, August 7th, 2009 at 9:38 am by: Tom Vanderbilt
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One-Way or Two-Way?

Via Roadguy comes this interesting and nuanced discussion of a planned conversion in Minneapolis from one-way to two-way streets, on what seems like former residential boulevards (Park and Portland) that were turned into de facto highways in the incipient motor age.

I could have written an entire chapter in Traffic about the one-way/two-way debates (like LCD and plasma, they each have their particular attributes), but of more immediate concern to me here is the idea that every conversion I’ve heard of recently is from one-way to two-way. I wonder if the tide of planning orthodoxy has fully shifted, or are there any big two-way to one-way conversions going on as I write?

Posted on Thursday, August 6th, 2009 at 10:21 am by: Tom Vanderbilt
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How New York Might Have Looked

In recently doing some research on the historical traffic problems at Times Square, I came across the article above in the New York Times, circa 1911, which described the call of one Charles R. Lamb (formerly of the Municipal Art Society) to have another diagonal boulevard built in Manhattan, originating at 34th street — apparently in a massive, terrifying traffic circle — and running up to a plaza at 53rd Street.

Interestingly, the article makes the following claim, which runs precisely counter to what we now think of the way the diagonal of Broadway functions:

“The real difficulty with New York is this: that the only diagonal we have is Broadway. You can easily see the force of this point if you will remember that every man instinctively takes an angle street if he can because it makes the least distance. The automobile man does it: so does the truck-man; so does the pedestrian; everybody does.

And to just the extent that a person can turn from an angle, he will do it. You can see that at Times Square where Broadway cuts across Seventh Avenue. You can see it in Washington where the men that planned that city were wiser than the men that planned ours and where they cut frequent diagonal avenues with spacious circles at regular intervals. Just imagine what New York would be if the Times Square situation were repeated so frequently that a man could make his choice of taking an angle street or going around the block whenever he felt like it.”

Imagine indeed…

Posted on Wednesday, August 5th, 2009 at 6:41 am by: Tom Vanderbilt
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Wu Jiao Chang

After my recent Slate article about roundabouts, part of which I spent delineating the differences between the traffic circles of yore and the modern roundabout, reader Anders sent in this photograph of this startling construction in Shanghai, decidedly the former category. He writes:

This is a traffic circle in the Yangpu district of Shanghai called Wu Jiao Chang, where 5 roads intersect (which is the basic meaning in Chinese). Every intersecting road has a light for entering the circle while there are also traffic lights within the circle.

A bit of further digging notes that the colored form in the center is the work of an artist named Zhong Song:

According to the artist himself, he has engaged the site’s knotty condition: “there are five roads leading to the plaza, with a highway overpass on top, and a subway line underneath. There are three different levels of infrastructure, creating a complex fabric that affects the pedestrian nature of the area. So, the question was, how do we add the pedestrian element so people will animate the five different streets?”. To accomplish this task, the artist enveloped the 105-foot-wide overpass in an ovular steel frame clad with aluminum. Measuring 348 feet long, 157 feet wide, and 82 feet tall, it cloaks cars speeding along the overpass.

Has anyone spent time in this place (I missed it while in Shanghai)? When was it built? How does one even get to the center, to enjoy the animated neon oval? (I can’t tell but there seems to be pedestrian underpasses, which might make this some weird modern version of Eugene Henard’s famous carrefour a gyration in 19th century Paris).

Posted on Monday, July 27th, 2009 at 2:03 pm by: Tom Vanderbilt
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Are Roadside Memorials a Hazard?

This is an evergreen issue in highway safety, one that the New York Times has recently opened for debate. I brought up the issue recently after a trip to Montana, which permits a standardized memorial for road safety purposes (but does not look kindly upon additional embellishments).

And the issue has come up again in Australia, in a suburb of Melbourne, where, if this account from The Age is to be believed, a roadside memorial to the death of four young drivers has, in a moment of supremely tragic irony, led to the death of another young driver, a mere two weeks later. The memorial has since been removed, to some controversy.

But the first thing to note is that this is one of those enduring gray areas in traffic safety; as far as I know, there’s been no peer-reviewed study of the crash risk posed by roadside traffic memorials. This doesn’t stop people from offering firm opinions, but as far as I can tell, the science is nil. We don’t even really know the distraction effects of memorials, or if they are are any greater than that posed by billboards, signs, people walking their dogs, etc. (none of which carry, as memorials do, at least the potential to actually encourage safer driving). That said, one can also make the argument that intersections are places where drivers have to make often complicated decisions, and to have a large memorial engaging their attention at that location may not be a good idea. And what their attention is being engaged by is a question to consider as well. One reason is related to a theory proposed by psychologist Steven Most (who is quoted in Traffic): “Emotion-induced blindness.” As The Economist described his study:

Dr Most made this discovery while studying the rubbernecking effect (when people slow down to stare at a car accident). Rubbernecking represents a serious lapse of attention to the road, but he wondered if the initial reaction to such gory scenes could cause smaller lapses. The answer is, it does. What he found was that when people look at gory images—and also erotic ones—they fail to process what they see immediately afterwards. This period of blindness lasts between two-tenths and eight-tenths of a second. That is long enough for a driver transfixed by an erotic advert on a billboard to cause an accident.

It is entirely possible that something like this could have occurred in the Australia case, the memorial inducing a moment of emotion that triggered some kind of attentional blindness, though there is really no way to know for sure what was going on in the mind of the driver, or what she saw or didn’t see, as she made the turn. Reading a bit deeper into the article, a couple of other things stand out. One is that the speed limit of the road was 80 KPH — it is now going to be lowered to 70 KPH. The previous speed limit is roughly 50 MPH, which, judging by the Google Earth photograph below, seems incredibly high for a road bordering a quite residential area.

I don’t know the area in question, but given the article’s description, it seems a sort of once-rural area that is being increasingly developed.

A worker at the Foodies Service Station, at the intersection, said there was an accident every two weeks and traffic lights were desperately needed. Hermiz Toma, who has worked at the station for eight years, said in the past three to four years the accident rate had spiked as the neighbourhood had expanded. “The area is becoming busy with new buildings and more cars and it is too hard for people to get from Ormond to Hallam Road,” Mr Toma said.

It seems, in other words, like one of those “in-between areas,” as Hans Monderman put it, in Traffic: Neither limited-access highway nor low-speed residential area. Instead, you have a high-speed road going through an increasingly dense environment — the “traffic world,” as Hans put it, plunging like a knife into the social world. The authorities in question now plan to install a traffic light at that particular intersection, a typical standard response to a serious crash. Will they do so at every intersection along that road, or only the intersection where the crash occurred? Is a traffic light an appropriate response? Would a road diet on that very wide-looking road, and a series of roundabouts, have created an entirely safer situation — i.e., the truck would have had to slow to navigate the intersection — that might have prevented the first deadly crash that inspired the memorial, as well as the following fatal crash that is now being blamed on the memorial?

I’d be curious if anyone can shed any further local knowledge — or has thoughts about memorials in general.

(Thanks to Gerry)

Posted on Tuesday, July 14th, 2009 at 4:21 pm by: Tom Vanderbilt
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No One at the Wheel

Transportation Alternatives has released an important new report, titled “No One at the Wheel,” which I’ll be commenting upon further once I’ve had the chance to read it in its entirety. But the above graphic hints at some of the noteworthy and troubling findings.

Posted on Tuesday, July 14th, 2009 at 1:23 pm by: Tom Vanderbilt
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Red Yellow Green

In Traffic I make a passing mention of the evolution of traffic light sequences:

Others wanted the yellow light shown before the signal was changing to red and before it was changing from red back to green (which one sees today in Denmark, among other places, but nowhere in North America).

Reader Claire writes in to note that she remembers this sequence being used in the U.S.:

I distinctly remember passing through signals of this type on arterial streets in Chicago between 1977 – 1983. They were mostly located west of the L tracks on arterial streets like Belmont, Armitage, Fullerton, Devon, and Ashland.

Now, I didn’t say they were never used in the U.S., just that they aren’t anymore — although I may be wrong here and I’d be curious to see an example. She helpfully points us to Willis Lamm’s Traffic Signal page, which contains video examples of these “really funky signal phases.”

I’ve seen international studies on the potential problems with the red-amber-green phase, but haven’t really heard or read an account of why these phases vanished in the U.S. (though I’m sure the information is out there, in some back issue of the ITE Journal). I can imagine there are pedestrian issues, not to mention intersection clearance issues. And given that hardly anyone drives a manual shift in the U.S., one of the perceived virtues of that system is now largely lost here, like an old piece of slang no one uses anymore.

Posted on Tuesday, July 14th, 2009 at 12:01 pm by: Tom Vanderbilt
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When You Truly, Absolutely Need Stop Sign Compliance

Here’s an extreme case of where stop sign compliance is really a life or death situation: U.S. military checkpoints in Iraq and Afghanistan. A fascinating brief in the New Scientist notes that:

When a vehicle approaches a checkpoint at speed, ignoring warning signs to slow down, troops do not know whether the driver is simply careless or a suicide bomber. They need a clear and harmless way of forcing drivers to stop.

Green laser “dazzlers” were created for this purpose, the magazine notes, “but at short range they can damage the eye, and a number of US troops and civilians have ended up in hospital with eye injuries after ‘friendly fire’ incidents.”

But a more benign solution is in the works:

Now the US Department of Defense’s Joint Non-Lethal Weapons Directorate (JNLWD) in Quantico, Virginia is developing a pulsed laser designed to prevent eye damage. Its wavelength means a portion of the light is absorbed by the vehicle windscreen, vaporising the outer layer of the glass and producing a plasma. This absorbs the rest of the pulse and re-emits the energy as a brilliant white light that is dazzling but harmless. Because the light is emitted from the windscreen, the effect on the driver’s eyes should be the same regardless of the vehicle’s distance from the laser.

I don’t suppose this sort of thing would fly on civilian roads; but, for example, as a can’t-miss traffic light, or a way for police to disable drivers in pursuits, or a form of extreme neighborhood traffic calming…

Posted on Tuesday, July 14th, 2009 at 6:06 am by: Tom Vanderbilt
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The Problem With Signalized Intersections

This video demonstrates in startling fashion the design and safety problems of signalized four-way intersections (not to mention large pickup trucks).

(via The Huffington Post)

Posted on Tuesday, July 14th, 2009 at 5:56 am by: Tom Vanderbilt
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A Few Thoughts About ‘On a Crash Course,’ by Miller & Zaloshnja

I’ve finally gotten around to reading ‘On a Crash Course,’ a report by Ted Miller and Eduard Zaloshnja that’s been getting a lot of play in the media. As the Post summarizes:

Bad highway design and conditions are a factor in more than half the fatal crashes in the United States, contributing to more deaths than speeding, drunken driving or failure to use seat belts, according to Ted R. Miller, who co-wrote the 18-month study released yesterday.

Road-related conditions were a factor in 22,000 fatalities and cost $217.5 billion each year, the study concludes. By comparison, Miller said, similar crashes where alcohol was a factor cost $130 billion, speeding cost $97 billion and failure to wear a seat belt caused losses of $60 billion.

Despite being sponsored by a consortium of road-building concerns, who naturally have a vested interest in highway improvements, there are some interesting and commendable points raised, or at least implied. The first is, given that road crashes bear a larger societal cost than congestion, we should be focusing whatever stimulus dollars (too many, in my opinion) are going to roads on indeed bringing up deficient roadways to modern safety standards, rather than building new roads. Unfortunately, this does not seem to be the case.

Another thing that caught my eye was the high figure of deaths attributed to roadway condition: “Roadway condition is a contributing factor in more than half—52.7 percent—of the nearly 42,000 American deaths resulting from motor vehicle crashes each year and 38 percent of the non-fatal injuries. In terms of crash outcome severity, it is the single most lethal contributing factor—greater than speeding, alcohol or non-use of seat belts.”

This surprised me, as any number of previous studies, including the famous (and much more comprehensive) Indiana Tri-Level Study, as pictured below, paint a different picture of causality.


Posted on Tuesday, July 7th, 2009 at 3:46 pm by: Tom Vanderbilt
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The Ancient Art of Traffic Calming

When I wasn’t watching a bit of Tour de France, or playing backyard badminton, I was hammock-bound this weekend (I was clearly out of town, as my Brooklyn apartment has neither yard nor hammock) with Mary Beard’s wonderful book The Fires of Vesuvius: Pompeii Lost and Found. Beard, a Cambridge classicist who also blogs, leaves no layer of pumice unturned as she probes the “ordinary life” of the lost town. Not surprisingly, there’s a bit about streets, and the still ongoing tension between the externalities of wheeled traffic and the other functions of urban spaces.

The streets of Pompeei could be closed to wheeled transport by simple devices: by large stone bollards fixed in the roadway, by the placing of fountains or other obstructions across the traffic path, or by steps or other changes of level that were impassable to carts. Every one of these was used to ensure that, at least in its final phases, the Pompeian Forum was a pedestrian area. We should put out our minds any fanciful reconstruction of the central piazza criss-crossed by chariots and carts. Each entry point to the Forum was blocked to wheeled traffic…

Pompeian traffic was then reduced or, in modern terms, ‘calmed’ by the creation of cul-de-sacs, and other kinds of road block. But there remains the more general problem of narrow streets and what would happen if two carts should met in those many roads which were wide enough only for one. Needless to say, reversing a cart drawn by a pair of mules, down a road impeded by stepping stones, would have been an impossible feat. So how did the ancient Pompeians avoid repeated stand-offs, between carts meeting head-to-head? How did they prevent a narrow street being reduce to an impasse?

Well, I don’t want to give the whole thing away — read the book!

Posted on Monday, July 6th, 2009 at 8:18 am by: Tom Vanderbilt
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Another item of interest I had come across in Joe Moran’s book was the “Conemaster,” an automated device for laying down traffic cones on the highway. That’s a U.K. product, but there are others, as the video — of a “single operator lane closure system” — above shows. Given the hazards posed by drivers to people working on highways, this is a clearly useful device. A bit of background:

Currently, traffic cones are deployed by a person riding on the exterior of a modified vehicle. This person is typically either standing in a basket at the end of a truck or sitting near ground level between the axles of the customized cone body truck. On the current Caltrans cone truck, two horizontal stacks of cones are fed by conveyor to a worker who then places or retrieves the cones while another person drives the vehicle.

In 1990, The State of California paid out $36,000 in injury claims related to manual cone laying. This increased over 10 time in four years to $321,000 in 1994. Available statistics suggest that this trend of increasing costs is continuing.

The AHMCT Center has developed a machine that can automatically place and retrieve traffic cones. This machine fits onto existing Caltrans traffic cone trucks and all operations are controlled from within the cab by either the driver or a second operator.

A typical lane configuration uses 80 traffic cones for each 1.5 miles of lane closure. Traffic cones come in various sizes up to 36 inches high. Caltrans uses a 28 inch high cone that weighs 10 pounds. When cones are being carried to and from stacks on the bed of a truck, personnel are restricted from carrying more than 3 cones at one time and this operation of manually transferring the cones is often performed on the roadway.

Now, where have our robotic bollards gone?

Oh, and by the way, it cleans up after itself too.

Posted on Monday, June 29th, 2009 at 1:30 pm by: Tom Vanderbilt
Comments Off on Robo-Cones. Click here to leave a comment.
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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