As opposed to a "protected" left turn, in which a solid green arrow gives a driver the complete right of way in a left-turn lane, a "permitted" left turn is often allowed by a confusing hodgepodge of signals, and drivers may have to pick their way through narrow windows of oncoming traffic.

This difficult driving maneuver, which is played out millions of times a day around the world, is fraught with risk for unwary pedestrians, who too often appear to be an afterthought.  The danger is much higher than had been realized, experts say.

"There are far more pedestrian crashes in marked crosswalks than anywhere else on roads, and pedestrians already have a false sense of security," said David Hurwitz, an assistant professor of transportation engineering at Oregon State University. "This study found that one key concern is permitted left turns."

Photograph by Laura Sandt,  Portland, Oregon. The Pedestrian and Bicycle Information Center (PBIC). The caption noted that the bike lane curves out of the way of turning transit.