Cautions about Car Telephones and Collisions

Lawmakers in many countries are waiting for direct evidence that the use of cellular telephones in cars contributes to roadway collisions. In this issue of the Journal, a study of collisions in Toronto provides the first such evidence.1 By comparing the times of cellular-telephone calls, obtained from billing data, with the times of collisions, Redelmeier and Tibshirani estimated that the risk of a collision was between 3.0 and 6.5 times as high within 10 minutes after a cellular-telephone call began as when the telephone was not used. Our further analysis of their data confirmed that the risk more than doubled . . .