Comments on: A Few Thoughts About ‘On a Crash Course,’ by Miller & Zaloshnja

By: Bike Accidents

Bike Accidents — Fri, 11 Jun 2010 10:11:58 +0000

Its a catch 22 kind of situations here … we cannot have better roads overnight and maybe the need is for safer corridors on existing infrastructure, and better implementation of a rigid and strict monitoring system which helps in reducing error prone driving and also acts as a deterrent for those considering to try out living a video game kind of scenario in real life. After all safety is a must and needs improvement globally.

By: Ted Miller

Ted Miller — Thu, 17 Sep 2009 21:03:25 +0000

Someone just brought this commentary to our attention. We may reply further to some of the many thoughtful points raised here later. But I wanted to put a few thoughts out there quickly. First, a version of this study has been peer-reviewed; it was in press before we released the estimates. Second, the Tri-Level study has long been criticized for over-stressing the human side and underemphasizing vehicles and environment. Nevetheless, if we looked only at crash causation and not at crashes made more severe by road deficiences, we would get roughly 35% as Tri-Level did. What tilts the equation is that 46% of fatal crashes and 40% of serious to critical injury crashes (but only 10% of other crashes) involve harmful contact with a non-breakaway medium or large pole or with a large tree or first harmful contact with a bridge. That was not true in 1990, but cars have become safer, drivers more sober, and the roadside therefore has emerged as a more important factor. The relative risk for those three kinds of crashes being serious-to-fatal is around 4 so we attributed 75% of the serious-to-fatal cost to roadside deficiencies (being careful not to double-count crashes we already had said were related to roadside deficiencies. I was quite surprised at what a large factor non-breakaway poles have become. Those are totally fixable hazards.
Finally, I wanted to give you my take on our study, which is not that dissimilar to Tom’s. The driving environment is very forgiving. Drivers often make minor errors. They also speed, they get distracted, they drive drowsy, or they take one drink too many. When the roadway is deficient, those errors are more likely to cause a crash and crashes that occur are more likely to result in serious injury or in death. Although behavioral factors are involved in most crashes, avoiding those crashes through driver improvement and enforcement requires reaching millions of individuals and getting them to sustain best safety practices. It is far more practical to make the roadway environment more forgiving and protective. Safer drivers and safer cars remain vitally important, but it also is critical to make the roads, bridges, and shoulders safer.
Ted Miller

By: Lee

Lee — Thu, 09 Jul 2009 12:58:19 +0000

If you reduce the risk in the environment people will just do risk compensation.

After they spent stimulus money paving over lots of brick roads (which were as perfect as brick can be) here in East Baltimore, we started getting lots of accidents where we never had any traffic accidents whatsovever before… in response to the complaints about speeding cars, they are now installing speed bumps everywhere. So now, instead of complaining about the brick roads, people are complaining about all the speed bumps, and the cars that speed from one speed bump to the next. Plus now they say they have to install more stop signs, lights, etc. However on the streets that are still brick, everything is just fine.

By: Dr. Leonard Evans

Dr. Leonard Evans — Wed, 08 Jul 2009 15:50:20 +0000

Potholes and rumble strips are similar safety devices that work in similar ways. Removing either reduces safety. There are many compelling reasons to keep the roads in good repair - but safety is not one of them. Replacing a rural two-lane road with an Interstate does reduce crash risk — but there are convincing reasons to not do this. The overwhelmingly dominant factor in safety is speed. Factors that increase speeds, like removing congestion or potholes, INCREASE fatality risk. A 1% increase in travel speed leads to a more than 4% increase in fatality risk.
Leonard Evans, author of “Traffic Safety” [www.scienceservingsociety.com/traffic-safety.htm]

By: Bossi

Bossi — Wed, 08 Jul 2009 13:27:11 +0000

As a traffic engineer, I approach my job with the firm belief that people *want* to drive in a safe & legal manner, but road design encourages them to disobey & disregard. That is, road design leads into the human factors. However, unlike the report, I hardly believe that straightening curves & widening clear zones is the answer… that’s the reason we’re in our predicament to begin with. In my opinion, the late Hans Monderman was spot-on with more context-sensitive designs reflecting the class of the roadway.

By: Christopher Monnier

Christopher Monnier — Wed, 08 Jul 2009 04:33:03 +0000

Is the problem here lack of safety engineering, or lack of behavioral engineering?

I think the problem is in the perspective of whom roads should serve. In Sweden (and Europe, in general), it seems that the default road user (in urban areas, at least) is pedestrians, and cars must play second fiddle. In the US, the bias is skewed far in favor of cars over pedestrians. The American mentality is that roads are merely conduits that exist to shuffle vehicles through as quickly as possible. Pedestrians, congestion, traffic calming measures…these are all obstructions to what seems to be a God-given right for cars to get from point A to point B as soon as possible.

By: Rich in CO

Rich in CO — Tue, 07 Jul 2009 22:37:09 +0000

This is a commisioned, non-peer reviewed “report”, which concluded that only 19.1% of fatal accidents were related to “road conditions” until the researchers decided that in any fatal accident where a bridge, a pole or a tree was involved the bridge, pole or tree had a 100% probability of contirbuting to the fatality. (Letting the fact that many of these things are stuck with non-fatal results slide). Even if we buy their argument that it should be impossible to strike a tree or a pole (those traffic signal poles are going to be a bit difficult to remove - they are often “involved” in fatal crashes when the crash occurs in an intersection) the authors assertion that properly designed bridges would not be involved in crashes is silly on its face.

It is just as valid to point out that 79.9% of fatal crashes (according to the same report, in table A-11, page 33) occured in the absence of “road-related conditions”. Unless we accept (I don’t) that at least 79.9% of travel occurs on roadways meeting all standards (better than that, not just a forgiving roadside, but one where hitting trees or posts is actaully impossible) then apparently we can conclude that roads built to high standards are over-represented in fatal accidents.

What’s the old saw about liars and figures?