Archive for July 14th, 2009

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)

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.

The answer, interestingly, is October. That’s what Michael Sivak concludes in a new paper in Traffic Injury Prevention.

March has the lowest fatality rate (8.8 per billion kilometers), followed by February and April. Thus, the risk of a fatality per distance driven in October is about 16 percent greater than the risk in March.

Sivak notes that the factors for seasonal variation in crash risk are, as one might expect, complex — ranging across everything from alcohol consumption to “duration of darkness” to leisure driving (“Leisure driving, which occurs more frequently on unfamiliar roads, at higher speeds, at night, and under the influence of alcohol, is riskier than commuter driving”) to weather (“Inclement weather (e.g., snow and ice), everything else being equal, should increase the risk of driving. However, because
inclement weather also leads to general reductions in speed, the net effect is not clear.”)

In light of all these, October seems a bit strange; not as much vacation driving as during the summer, inclement weather hasn’t kicked in in most places, though the onset of earlier darkness might be an issue (not to mention the outlier day of Halloween).

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.

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…

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)

Coming home late last night from Newark Airport, I was passed by three ‘Ninja’ cyclists doing at least 90 mph, and couldn’t help but think of a paper I had read on the flight, “Donorcycles,” by Stacy Dickert-Conlin, Todd Elder and Brian Moore, which argues there is a link between higher organ-donation rates and the lack of a helmet law in certain states. Reading the last paragraph in particular somehow really just put me in mind of Thomas Carlyle’s famous dictum about economics being the “dismal science”:

Understanding the unintended consequences of helmet laws allows for more informed
policymaking by providing a more complete picture of the costs and benefits involved. Although our estimates point to a sizeable effect of helmet laws on motor vehicle accident-based organ donations, the repeal of all helmet laws as a measure to reduce the severe shortage of organs in the U.S. would be ineffective in isolation, primarily because over 80 percent of organ donors die due to circumstances unrelated to motor vehicle accidents. Our preferred estimates imply that nationwide elimination of helmet laws would increase annual organ donations by less than one percent.