CONTACTTRAFFICABOUT TOM VANDERBILTOTHER WRITING CONTACT ABOUT THE BOOK

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.


Of course, this could be due to the difference in talking about what causes crashes, and what causes crashes that turn out to be fatal (this study, it should be noted, also relies on the “Large Truck Crash Causation Study” for data; it’s a well-regarded study, but the obvious problem is that it studied large trucks, which obviously have different characteristics than cars, and do the bulk of driving in different environments). This gets at the philosophy of the “forgiving road,” i.e., that road users should not pay a fatal price for all-too human mistakes. And, as Leonard Evans observed in Traffic Safety, the factors involved in crashes do not often correlate to the best countermeasures; just because “human factors” cause most crashes, we should not always try to fix the problem at the level of human factors. “An effective analogy points out that finding that mailed items are damaged by the human factor of careless handling does not mean improved handling is the most effective countermeasure. Better packaging is far more effective.” Call it “forgiving packaging.” (Another analogy given to me was “fire-safe cigarettes”; e.g., we can spend a lot of money trying to educate people not to smoke in bed, or punish those who do, or we can simply make cigarettes that are less likely to lead to fires — yes this may lead to risk compensation but if the overall result is more safety it’s still socially useful).

But let us note that Evans adds: “It is changes in driver behavior that have the potential to make, by far, the largest improvements in traffic safety.” It is interesting in this regard to note that the states that the authors claim as having the worst road conditions (they’re mostly in the south) are the very same states that have some of the worst seat-belt wearing rates and some of the highest drunk-driving rates. Building safer roads isn’t going to change those numbers.

And yes, clearly there is room for making many of America’s roads safer; many is the time I’ve been driving down, say, Highway 17 in New York near Bear Mountain, and wishing there was a barrier between myself and the opposing lane of traffic, which might be carrying a texting teen or a nodding-off salesman. And as I noted recently from Montana, I’m all in favor of cheap solutions that don’t lead to riskier behavior (like rumble strips). But on the other extreme, is it really society’s responsibility to guard-rail every last rural mile of highway in America, tear down every roadside tree, so that the drunk driver doesn’t run off the road and strike an obstacle? (One might make the ethical argument that to keep the drunk driver alive in this case is simply to raise the risk that he will eventually crash into another driver).

Another problem (which Elana Schor already raised, partially in my behalf), is exactly what kinds of roads we’re talking about fixing, and how. As I note in Traffic, Eric Dumbaugh in particular has done work showing that in many cases, so-called “forgiving road” environments actually have the perverse effect of bringing more crashes than areas that, by traditional safety engineering standards, are presumed to be more safe. Tree-lined streets in this regard are not a hazard; rather, they are the safety device — if one drives at the contextually chosen speed (and again, if one does not, is it society’s burden to prevent the outcome?)

“Forgiving road” is a rather expansive term, in any case; one way to make a road more “forgiving,” for all its users and not just drivers, is to lower speeds. This gives drivers more time to react to their mistakes, gives them a more forgiving crash outcome, and also makes the crash more forgiving when they happen to strike a pedestrian or a bicyclist or indeed another car.

Many of the things recommended in the report — wider shoulders, clear zones, etc. — have little place in many urban and suburban residential environments, unless one wants to engage in the old dream of the modernist architects (which too many traffic engineers have tried to do) — i.e., to “kill the street,” as Le Corbusier said, fully segregating all uses, allowing a dense city with fast highways, as pictured below.

Futurama was a car-company sponsored world’s fair folly, of course, and cities that tried to approximate it are still paying the price (or rushing to fix their mistakes). But the results coming from places like Kensington High Street in London are that many of the so-called traffic safety improvements simply led to worse behavior, and in their absence safety numbers for all modes have unexpectedly improved. Commenting on Swedish traffic safety, Neil Pearce notes that their approach is built around different strategies for different environments:

How did the Swedes do it? Tough seat belt and helmet laws, to be sure. But they’ve also begun to remake their roadways. Red lights at intersections (which encourage drivers to accelerate dangerously to “beat the light”) are being replaced with traffic circles. Four-foot high barriers of lightweight but tough mylar are being installed down the center of roadways to prevent head-on collisions, and as side barriers at critical locations. On local streets, narrowed roadways and speed bumps, plus raised pedestrian crosswalks, limit speeds to a generally non-lethal 20 miles an hour.

We, on the other hand, try to engineer safety onto our lower speed roads, which then play host to routine excessive speeds. Is this is a big deal on roads with lower-speed limits? The following graph notes that a surprisingly high amount of traffic fatalities due to speeding occur on lower speed roads (typically home to the most pedestrians and cyclists). Is the problem here lack of safety engineering, or lack of behavioral engineering?

There’s another procedural item that bothers me about the study, which is the list of factors by which “road conditions” would be blamed for a crash. Among this list are predictable things like “surface defect” (although again, in New York City at least, these act as traffic calming safety devices) and “bad lane marking,” but then one also sees “narrow road” (what does this mean, exactly, that it wasn’t wide enough for two vehicles to pass; or that someone was driving too fast and clipped an edge, or too narrow for a large truck?), “icy conditions” (are we to build radiant heating under all roads?), “insufficient sight” (a number of studies have shown that drivers merely offset increased sight distance with increased speed), and so on — I could go on, and many of these are valid, to a point.

But where does “road factors” causality end? Does every left-turning crash that happens at an intersection without a protected left arrow come down to road factors? Better yet, does every intersection need to be replaced with a flyover, to prevent conflicts? Do we eliminate curves to prevent crashes, or keep roads straight and raise the risk of fatigue? Do we illuminate roads at night, thus putting more hazardous obstacles in the road by day? Once we finish all this work, the construction lobby can then move to every backyard in the U.S., and pave over the swimming pools which represent a very real health risk.

But in the list of road factors in this report, weirdly, one sees “congestion” coded as a road condition. So a perfectly engineered road is safe when empty but then mysteriously becomes dangerous when loads of cars decide to use it? Was this report merely a fig leaf for more building of new roads? Congestion is a social condition — rarely an engineering one — and one that could be easily avoided through any number of means (e.g., taking one out of five drivers out of a rush hour car and putting them in a carpool). In any case, Montana, a state with very little congestion, hosts the most fatalities per mile driven in the country — should we count “lack of congestion” as a causal factor as well?

It all goes back to what I like to call the “four Es” of traffic safety — engineering, education, enforcement, and exposure (on this last point, we largely have the poor economy, and the reduction in driving — and in certain types of driving — to thank for the lowest level of road fatalities since 1961). They are like legs of a table — pull one away, and things start to get wobbly.

This entry was posted on Tuesday, July 7th, 2009 at 3:46 pm and is filed under Risk, Roads, Traffic Culture, Traffic Engineering, Traffic safety, Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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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.

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Upcoming Talks

April 9, 2008.
California Office of Traffic Safety Summit
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May 19, 2009
University of Minnesota Center for Transportation Studies
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June 23, 2009
Driving Assessment 2009
Big Sky, Montana

June 26, 2009
PRI World Congress
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June 27, 2009
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July 13, 2009
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Royal Automobile Club
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Wisconsin Department of Transportation’s
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American Association of Motor Vehicle Administrators
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Wednesday, October 26, 2011
Attitudes: Iniciativa Social de Audi
Madrid, Spain

April 16, 2012
Institute for Sensible Transport Seminar
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April 17, 2012
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Centennial Plaza, Sydney
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April 19, 2012
Institute for Sensible Transport Seminar
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January 30, 2013
University of Minnesota City Engineers Association Meeting
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January 31, 2013
Metropolis and Mobile Life
School of Architecture, University of Toronto

February 22, 2013
ISL Engineering
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March 1, 2013
Australian Road Summit
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New York State Association of
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Rochester, NY

August 18, 2013
BoingBoing.com “Ingenuity” Conference
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September 26, 2013
TransComm 2013
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of State Highway and Transportation
Officials’ Subcommittee on Transportation
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