(LTBL:Chap 2a) Those Bothersome Bumps From Behind
The kind of separation between cars and bikes provided by bike lanes and next-to-the-road bike paths helps keep motorists from bumping into bicyclists’ back ends. However, these facilities do little to prevent the numerous kinds of collisions caused by the crossing and turning movements of both bicyclists and motorists. Bikeway critics, therefore, question whether overtaking motorists are enough of a threat to justify the effort to separate bikes from cars, considering that there may be side effects, such as hindering bicyclists’ movements and making crossing and turning more difficult, or even more frequent. This chapter will put through the ringer what we know about bump-from-behind collisions in hopes of squeezing out a reasoned understanding of these controversial car-bike crashes. (For convenience, I will use “car” to refer to any kind of motor vehicle.)
John Forester (1994) argues that you can get a clear answer to the overtaking-risk question by looking at crash statistics:
Kenneth Cross (1978), whose bicycle crash studies form the foundation for many of Forester’s arguments, paints what seems to be a different picture when he describes what he calls “Problem Type 13,” in which an overtaking motorist fails to see a bicyclist until it’s too late to avoid a collision:
These show that many more car-bike collisions (about 95 percent) are caused by crossing and turning maneuvers from in front of the cyclist than are caused by the car-from-behind-a-lawful-cyclist collisions that worry cyclist-inferiority believers so much. Furthermore, car-bike collisions are only about 12 percent of all accidents to cyclists. This combination makes the car-overtaking-a-lawful-cyclist in urban areas in daylight (which is the type of accident used to justify transportational bikeways) only about 0.3 percent of total accidents to cyclists (pp. 10-11).
So we have on the one hand an analysis that says the overtaking risk is negligible, and on the other hand an analysis that characterizes the overtaking collision as the most deadly of all car-bike crashes. A clearer picture emerges when we look more closely at Type 13 crashes and, first, at the study from which these statistics came.
Although seven other problem types occurred more frequently than Problem Type 13, this problem type must be considered one of the most important because it accounted for nearly one-fourth of all fatal accidents in the sample—three times as many as any other problem type (p. 72).