6.11 Bright bike lights. Will requiring bicyclists to use bright, high-intensity xenon lights mounted on the front and rear of the bike reduce accidents with cars by making bikes more visible?
(a) Briefly discuss the design of an experiment to help answer this question. In particular, what response variables will you examine?
(b) Suppose your experiment demonstrates that using high-intensity xenon lights reduces accidents. What concerns might you have about whether your experimental results will reduce accidents with cars if all bicyclists are required to use such lights? (Hint: To help you answer this question, consider the following example. A 1980 report by the Highway Traffic Safety Administration found that adding a center brake light to cars reduced rear-end collisions by as much as 50%. These findings were the result of a randomized comparative experiment. As a result, center brake lights have been required on all cars sold since 1986. Ten years later, the Insurance Institute found only a 5% reduction in rear-end collisions. Apparently, when the study was originally carried out, center brake lights were unusual and caught the eye of following drivers. By 1996, center brake lights were common and no longer captured attention.)