Car phones and car crashes: an ecologic analysis.

Some countries have regulations against using a cellular telephone while driving. We used ecologic analysis to evaluate cellular telephone use and motor vehicle collisions in a city without such regulations.We studied locations in Toronto, Ontario (n = 75) that were hazardous (total collisions = 3,234) and tested whether increases in collision rates from 1984 to 1993 correlated with increases in telephone usage over the same time interval.Locations with the largest increases in collision rates tended to have the smallest increases in estimated cellular telephone usage. Yet extreme assumptions about potential protective effects from cellular telephones failed to explain the magnitude observed.The effects of cellular telephones on driving ability are small relative to the biases in ecologic analysis. Claims from industry, which argue that cellular telephones are not dangerous based on ecologic analysis, can be misleading in the policy debate about whether to regulate cellular telephone use while driving.