Behavioral scientists at Wayne State University analyzed possible bias in a 1997 Canadian study and a 2005 Australian study, a university release said Wednesday.
In these studies cellphone billing records of people who had been in a crash were used to compare cellphone use just before the crash to the same time period the day or week before as a control window.
The problem with these studies, Wayne State researchers said, is that people may not have been driving during the entire control window period as assumed by the earlier study investigators.
"Earlier case-crossover studies likely overestimated the relative risk for cellphone conversations while driving by implicitly assuming that driving during a control window was full time when it may have been only part time," said Richard Young, professor of research in Wayne State's Department of Psychiatry and Behavioral Neurosciences. "This false assumption makes it seem like cellphone conversation is a bigger crash risk than it really is.
"Tasks that take a driver's eyes off the road or hands off the steering wheel are what increase crash risk," Young said. "Texting, e-mailing, manual dialing and so forth -- not conversation -- are what increase the risk of crashes while driving."