In Traffic, Tom Vanderbilt argues that Americans rely on a lot of road signs even though there is little to no evidence that having more signs increases the safety of drivers and pedestrians. As an example, Vanderbilt looks at the “children at play” signs:

Despite the continued preponderance of “Children at Play” on streets across the land, it is no secret in the world of traffic engineering that “Children at Play” signs—termed, with subtle condescension, “advisory signs”—have been proven neither to change driver behavior nor to do anything to improve the safety of children in a traffic setting. The National Cooperative Highway Research Program, in its “Synthesis of Highway Practice No. 139,” sternly advises that “non-uniform signs such as “CAUTION—CHILDREN AT PLAY,” “SLOW—CHILDREN,” or similar legends should not be permitted on any roadway at any time.” Moreover, it warns that “the removal of any nonstandard signs should carry a high priority.”…

If the sign is so disliked by the profession charged with maintaining order and safety on our streets, why do we seem to see so many of them? In a word: Parents. Talk to a town engineer, and you’ll often get the sense it’s easier to put up a sign than to explain to local residents why the sign shouldn’t be put up. (This official notes that “Children at Play” signs are the second-most-common question he’s asked about at town meetings.) Residents have also been known to put up their own signs, perhaps using the DIY instructions provided by eHow (which notes, in a baseless assertion typical of the whole discussion, that “Notifying these drivers there are children at play may reduce your child’s risk”). States and municipalities are also free to sanction their own signs (hence the rise of “autistic child” traffic signs)…

One of the things that is known, thanks to peer-reviewed science, is that increased traffic speeds (and volumes) increase the risk of children’s injuries. But “Children at Play” signs are a symptom, rather than a cure—a sign of something larger that is out of whack, whether the lack of a pervasive safety culture in driving, a system that puts vehicular mobility ahead of neighborhood livability, or non-contextual street design. After all, it’s roads, not signs, that tell people how to drive. People clamoring for “Children at Play” signs are often living on residential streets that are inordinately wide, lacking any kind of calming obstacles (from trees to “bulb-outs”), perhaps having unnecessary center-line markings—three factors that will boost vehicle speed more than any sign will lower them.

So the signs are more of a band-aid to a larger problem which Vanderbilt discusses more in his book: streets and roads are generally designed in America for cars to go fast rather than as structures that also accommodate pedestrians and other neighborhood activities. Signs can’t do a whole lot to reduce the effects of this structure even though citizens, local officials, and some traffic engineers continue to aid their proliferation. In a car-obsessed culture, perhaps we shouldn’t be too surprised by all of this: people want to be able to move quickly from place to place.

This all reminds me of the efforts of groups like the New Urbanists who suggest the solution is to redesign the streetscape so that the automobile is given a less prominent place. By putting houses and sidewalks closer to the street, planting trees near the roadway, allowing parking on the sides of streets, and narrowing the width of streets can reduce the speed of drivers and reduce accidents. Of course, one could go even further and remove all traffic signs altogether (see here and text plus pictures and video here).

I wonder if we could use Vanderbilt’s examples as evidence of a larger public discussion about the role of science versus other kinds of evidence. There may be a lot of research that suggests signs don’t help much but how does that science reach the typical suburban resident who is concerned about their kids playing near the street? If confronted with the sort of evidence that Vanderbilt provides, how would the typical suburban resident or official respond?