A Case of Lane Envy


Life in the fast lane is probably all in your head. That's the finding of a Stanford professor and his colleague, who used computer simulations to study drivers' perceptions of freeway traffic. Their conclusion: the infuriating sense that other motorists are zipping ahead is usually an illusion.

The miscue stems from the fact that cars tend to spread out when they're going quickly and bunch up when they slow down, according to Robert Tibshirani, a professor of health research and policy, and his co-investigator, Donald Redelmeier of the Universtiy of Toronto. So even when adjacent lanes are averaging the same speed, drivers end up spending much more time watching other cars whiz by. This leads to the incorrect conclusion that the other lane is moving faster.

A quirk of human perception explains much of this phenomenon. When you drive you tend to look forward rather than backward, which means that the cars you pass are out of sight (and therefore out of mind). Those that overtake you remain annoyingly in sight, a constant reminder that you seem to be falling behind. Also, Tibshirani and Redelmeier write in the September 2 issue of Nature, "a driver is more likely to glance at the next lane for comparison when he is relatively idle."

In one experiment, 120 driving students were shown a videotape of an adjacent lane of traffic. Seventy percent believed the cars next to them were going faster when they were actually going slightly slower on average. Sixty-five percent of the students said they would change lanes if possible. The lesson, says Tibshirani: resist risky lane changes. You may already be in the fast lane.