In the latest Atlantic, John Staddon, a professor of psychology at Duke, has an article on the dangers of road signs and speed limits:
The American system of traffic control, with its many signs and stops, and with its specific rules tailored to every bend in the road, has had the unintended consequence of causing more accidents than it prevents. Paradoxically, almost every new sign put up in the U.S. probably makes drivers a little safer on the stretch of road it guards. But collectively, the forests of signs along American roadways, and the multitude of rules to look out for, are quite deadly.
His argument rests on inattentional blindness, or the inability of the brain to focus to multiple things at the same time. Because all those traffic signs compete for the scarce resource of driver attention, he argues that drivers end up neglecting more necessary variables, like the car that stopped directly in front of them. Basically, when it comes to driving it’s not the Magical Number Seven (Plus or Minus Two): it’s the Magical Number One (Plus or Minus One). The conscious brain, while controlling a car, can only handle one (or perhaps two) things at the same time.
The article has a certain contrarian allure, but the statistics are not completely compelling. Staddon’s evidence consists mainly of the fact that fewer people die from car accidents in Britain, which seems to have a slightly simpler method of directing traffic. (As an American in Britain, I found all those dashed lines and tiny roundabouts utterly confusing. I often felt like Chevy Chase in European Vacation.) He also cites a few examples of high-density European streets (Kensington High Street, etc.) where traffic signs have been completely eliminated. The end result is a reduction in pedestrian accidents, although he doesn’t say whether there was also a reduction in overall traffic accidents.
Personally, I’d find the argument more compelling if Staddon had taken driver training into account. After a few months of driving, many of the basic skills of driving become utterly automatic. You don’t have to consciously think about stopping at a red light because your brain automatically responds to the cue. (I always find yellow lights dangerous precisely because they require drivers to make a deliberate decision.) A stop sign doesn’t consume a lot of computational space, since you know that the sign means “put foot on brake”. You don’t think about it, you just do it. While a world without traffic signs and speed limits might make driving more, um, interesting, I’m not sure that it’s wiser to count on the constant vigilance of everyone on the road. I feel safer knowing that the guy in the big truck yapping away on his cell phone, or the driver eating lunch while shifting, doesn’t need to be paying conscious attention to the road: their unconscious brain can obey the rules without them.