Archive for the ‘Traffic Engineering’ Category

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.

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.

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.

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.

Reader David sends in this reminder, via Failblog, that even the best systems cannot account for the behavior of every last driver.

For your late Friday perusal, via Gawker, apparently rogue asparagus are causing havoc on the streets in Hokkaido, Japan. I’ll leave the punchlines to you (this is almost like a photographic version of the New Yorker cartoon contest).

For an excellent case study of incredibly thoughtful and detail-oriented transportation planning — see a few of the details below — I recommend this dispatch by Meena Kadri, reporting from Ahmedabad, in the Indian state of Gujarat.

On board the buses the most applauded feature is the provision of at-grade boarding — a hallmark of the best BRT systems, whereby passengers enter and exit buses at raised station platforms, without having to climb or descend stairs. Not only does this improve accessibility for the elderly, challenged and very young; it’s also been hailed as a plus point by many saree-clad female passengers. The span of income groups using the service is immediately evident and signals one of the BRT’s biggest impacts in Ahmedabad. Even motorists are being lured by the efficiency of Janmarg. Raju Schroff, who owns a local factory, now takes the bus to work. As a result, he says, “My daily commuting time has been more than halved, and I arrive at work calm rather than hassled from being stuck in traffic.” Jagu Desai, a tribal laborer, affirms her appreciation of its speed and comfort, and she seems pleased that her views were as much of interest to me as Schroff’s. Voice announcements and LED displays in both Gujarati and English — also a new feature for public transport in the city — are appreciated by the diverse passengers. As bus operator Panchal Kirti reports: “Not only can deaf people watch and blind people listen but people who can’t read are not excluded from being informed. So everyone on board can relax till their destination is announced.”

Ahmedabad’s comprehensive planning has pushed well past the mere concept of BRT — right through to encouraging physical resilience and solidarity amongst bus operators. Driver Jintendra Patel recalls that the two-month training included daily yoga sessions. “Yoga helps maintain calm and focus while driving,” he says, “and it counters the back problems that develop from sitting for long periods.”

I never really had a mantra for the Traffic book, the way Michael Pollan does: Eat food, not too much, mostly plants.

I tried to think: Drive safer, not so much, mostly walk (ok, that’s for New Yorkers). But you get the picture.

I noticed a few people responded to an offhand comment I made in the Streetfilms interview: “It’s too easy to get a license in this country, too hard to lose one.”

By this I mean our driver’s education and licensing system is in need of a number of reforms — we treat driving like a right, as in voting — and the newspapers (and courts) are filled with recidivist drivers. Read a random article about a fatal crash, and I’ll be you, that by about the sixth or seventh paragraph, you’ll begin to see examples of previous incidents or some underlying pattern of behavior that seriously undermines the “accidental” nature of any crash (e.g., the driver in the Taconic minivan crash). And yes, I am aware that many people with suspended licenses simply drive without a license, and yes, we need to look in many cases at the behavioral questions, yadda, yadda, yadda, but why we should continue to legally pander to people with a reckless disregard for human life is beyond me.

I was thinking of this again while watching, in Edmonton, a poignant talk by Melissa Wandall, whose husband was killed by a (repeat) red-light runner (the red-light law she’s worked for has just cleared the Florida senate; and despite what you often hear from the fringes of the right, most people, when polled, actually support such devices, when used judiciously). The offending driver already had 10 points on her license, a number of which kept getting bumped down by visits to traffic schools (the efficacy of which has been seriously called into question by several studies). Shockingly, she’s back on the road today.

Let’s go back to John Stuart Mill: “The only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others.”

It’s that ‘civilized’ bit I sometimes wonder about these days.

Via Brownstoner, I couldn’t help be horrified by the above aesthetic outrage, which seems like some sinister prelude to paving with asphalt (or else the paint fumes are getting to the crew). But I was struck by the comments: People really do seem to sincerely believe that there is a need for yellow dividing lines on presumably low-speed (particularly since they’re Belgian-blocked) streets, as if the mere fact that they were there was proof enough of their rationale and safety.

It’s amazing how our instinct fools us here. But, sorry folks, per your comments, yellow dividing lines aren’t going to keep your children safe, aren’t going to prevent crashes, aren’t going to magically keep drivers from swerving over into the other lane — the only effect that they’re going to have on driver behavior is to increase their speed (and hence raise danger for everyone) and even narrow their passing distance, as they grow confident in the delineation of their space. Dividing lines have absolutely no place on narrow, slow-moving, pedestrian-crowded urban streets. Save it for the highway.

If you want to know why pedestrian fatalities dominate the global traffic safety picture, this CNN clip from Cairo is one of just many places you could start. And please, Cairo, don’t make the mistake of building pedestrian overpasses and underpasses to “fix” the problem.

(thanks vagabond)

Sorry, one of my favorite bits from Henry V. But reader Matt writes in with a confusing (at least to him, and to me upon first glance) yield situation at an intersection in Pennsylvania (Google Map it at: “matsonford road, west conshohocken pa.” Given the mixed messages of the signage, what sayest thou, readers — will you yield?

Matt lays out the scenario below:

When I saw the headline, I thought it was referring to where the Santa Monica freeway intersects with the 405, but alas, it’s a novel interchange configuration, suitable for the Slough-ey, office-park-ey, pedestrian-free places of the world, perhaps some kind of next-century CFI.

(thanks Phil)

Via today’s New York Times:

At relatively slow rates of flow, turbulence is intermittent — it’s pushed along, Dr. Hof said, by smooth-flowing fluid behind it. By studying flows in a special glass pipe and modeling them on a computer, Dr. Hof and his colleagues realized that introducing an eddy into this smooth-flowing zone would eliminate the turbulence in front of it. “One turbulent eddy kills the other,” he said. As long as the pipe is straight, the flow should then remain smooth.

One wonders about any potential analogies to traffic here — the not quite perfect comparison that springs to my mind is the work, via people like Dirk Helbing and Serge Hoogendoorn, that shows in pedestrian escape modeling that introducing an obstacle into an exit opening actually improves the rate of discharge.

Any hardcore flow/sim types have any thoughts?

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:

(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.

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.

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.

Via This is London, the London borough of Islington is going to ramp up its number of 20-mph zones:

Islington council has agreed to introduce the limit in January to cut accidents, congestion and pollution. More than 150 miles of road will be affected, with motorists able to drive at 30mph on just 15 out of 1,420 streets…

In London, 31 of the 33 councils have introduced a total of 400 20mph zones. In Islington half of the roads already have the limits.

Rather than rote anti-jaywalking campaigns and the like, it’s nice to see some sanity entering the issue of urban speed. The recently released findings on pedestrian safety in cities, which again found Florida hogging several of the most-dangerous spots, speak to this; it’s not uncommon, in cities like Orlando, to see 40-mph zones in dense, pedestrian-heavy areas.

The device at right — the “Plant Lock,” for locking bikes, not plants — was new to me.

It’s one of a number of features employed in a so-called “DIY Street” in the East End of London.

Writes the Guardian:

Getting cars cars to slow down instead of racing through backstreet rat runs benefits everyone from cyclists to residents. But a windswept street on a November night in the East End of London is not the first place you’d expect to find inspiration for how to do that – not only cheaply but also with the total approval of the people who live there.

“We were expecting a 20mph sign and we got all of this!” a local told me.

More on the project here.

London’s Oxford Circus is one of those Yogi Berri-esque ’so popular no one goes there anymore’ sorts of urban spaces — I once did a little bit there for the BBC with Scottish-Sikh funnyman Hardeep Singh Kohli on “pedestrian rage” on the overcrowded street. It’s just gotten some relief in the form of a diagonal crossing (i.e., “scramble”), modeled on the crossing at Hachikō Square in Shibuya, Tokyo, a place one can easily lose a few hours just watching the action from a nearby donut shop). The video above describes the dynamics and shows the “before.” The impressive “after” can be viewed here.

Notes the BBC:

In homage to its Far Eastern inspiration, Mr Johnson struck a two-metre high cymbal as Japanese musicians played taiko drums.

A giant X, in the form of 60m (196ft) of red ribbon was also unfurled by devotees of cult Japanese Manga characters dressed in colourful costumes.

As with elsewhere in the city, pedestrian barricades have been removed (”giving shoppers and workers that visit annually around 70% more freedom to move,” notes the BBC).

I don’t know precisely when the first diagonal crossing was unveiled, though its popularity is certainly linked to Henry Barnes, NYC’s former traffic capo, who first unveiled it in Denver (where it earned the name ‘Barnes Dance’; he himself noted it had been tried elsewhere previously).

Here’s Barnes from his memoir, The Man with the Red and Green Eyes:

As things stood now, a downtown shopper needed a four-leaf clover, a voodoo charm, and a St. Christopher’s medal to make it in one piece from one curbstone to the other. As far as I was concerned–a traffic engineer with Methodist leanings–I didn’t think that the Almighty should be bothered with problems which we, ourselves, were capable of solving. Therefore, I was going to aid and abet prayers and benedictions with a practical scheme: Henceforth, the pedestrian–as far as Denver was concerned–was going to be blessed with a complete interval in the traffic signal cycle all his own. First of all, there would be the usual red and green signals for vehicular traffic. Let the cars have their way, moving straight through or making right turns. Then a red light for all vehicles while the pedestrians were given their own signal. In this interim, the street crossers could move directly or diagonally to their objectives, having free access to all four corners while all cars waited for a change of lights.

It’s hardly common, but does pop up in places with extraordinary pedestrian volumes or some other special circumstances, as in the historic-entertainment district of San Diego, where fellow INFORMS attendee Sean Devine snapped the photo below (alas, I didn’t experience the crossing myself, as I was out looking at seals).

Here’s another one, in Toronto, captured in time-lapse glory.

Scramble from Sam Javanrouh on Vimeo.

(thanks James)

Usually Staten Island’s in the news for its law-averse drivers, but here’s a different take: Renegade homegrown traffic engineers.

You have to love the irony.

Up went the Gatsometers, the Dutch brand that dominates the speed camera industry. Named after founder Maurice Gatsonides, a famous race car driver who developed the first speed monitoring system more than 50 years ago to help himself improve his speeds around corners, the early Gatsometers were rudimentary — cars ran over a wire, triggering a stopwatch that shut off after a second wire was tripped.

From a reasonably measured piece in the Washington Post.

More on Gatsometers at Slate.