Archive for July 10th, 2008

A few readers have asked me what I thought of “Distracting Miss Daisy,” an article by Duke University psychologist John Staddon in the current Atlantic (the full text is past the jump).

To briefly summarize, Staddon, who has driven in both the U.K. and the U.S., thinks American drivers suffer from a surfeit of traffic signs and speed limits. “The more you look for signs, for police, and at your speedometer, the less attentive you will be to traffic conditions.” He argues this helps explain the superior traffic safety record of the U.K.

On the whole, I was quite sympathetic to the spirit of the article, which was lively and well-argued — indeed, it visits a number of themes and places mentioned in my book (which has, for example, a section called “The Trouble with Traffic Signs”). His line, “we spend a lifetime on the roads after we get our licenses, and we’re being trained by our experiences every day,” could serve as a summary of Traffic. And as someone who recently took, as an experiment, a U.K. driving test (I’m writing an article about this), I’ve got my own opinions about comparative driving culture in the U.S. and the U.K., some of which are in line with Staddon’s point of view.

There were a few points in the article I thought deserved discussion, however.

1.) He says that in his experience, people “drive faster” in Britain. This just shows, I suppose, how subjective experience is. I challenge anyone to spend a week taking black cabs in London, and a week taking Yellow Cabs in New York City, and report a higher average velocity in the former. Also, the default speed limit in England of “lit, urban roads” is 30 mph. I’ve been in U.S. cities, in fairly urbanized areas, with (unobeyed) 40 mph limits. While we’re on the subject of limits, he does not mention in his piece the widespread deployment of speed cameras and red-light cameras in the U.K., two technologies which would seem “designed to control drivers and reduce their discretion” — a charge he makes against U.S. traffic safety efforts.

2.) He rightly invokes “risk compensation” in discussing why safety improvements in cars do not often produce the desired results: The safer people feel, the more riskily they act. But a bit later, he notes, “a particularly vexing aspect of the U.S. policy is that speed limits seem to be enforced more when speeding is safe.” (e.g., a sunny day). But is this not a form of risk compensation in itself? After all, most crashes occur during the day, during normal weather — the times we no doubt feel safer. As Leonard Evans notes in Traffic Safety, nearly 85% of fatal crashes happen on dry roads. There’s no such objective, quantifiable thing as a “safe” speed in traffic — plenty of people have died driving at the proper “design speed” of roads, while many children have been killed in driveways by cars going under 5 mph. The only thing we scientifically know is the higher the speed at which you collide with something, the greater the physical damage, and greater the risk of dying.

3.) And on the subject of speed, I am skeptical of Haddon’s claim that “looking at your speedometer” is an important form of distraction on the roads. First, I’m not sure how much time is actually spent looking at speedometers (in one study, drivers were asked, after they went through a slow school zone, how fast they were driving, and their estimates were wildly low). The second is that experienced drivers typically have a lot of spare cognitive workload, plenty for quick glances at gauges — and any minor distraction from a speedometer pales with the demands of, say, cell-phone conversations.

4.) I was interested that he notes that he finds roads “generally wider” here, which one might think would make things safer. In my U.K. driving test, taken in suburban London, I was quite surprised to find how often, on small residential streets, I had to pull over to let another car by. In general, I found road geometries tighter (and I was driving a fairly small car). But this is one of the ongoing debates in traffic safety: Making roads wider means you have less chance to bump into someone, but it also means you’re likely to drive faster. The experiments in which traffic control have been taken away (e.g., Drachten, Poundbury) only work because they are happening at very slow speeds, where the logic of human interaction, and not traffic engineering, take over.

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