A new study from Wayne State University claims early research about in-vehicle cellphone use may have exaggerated the risks of talking on a cellphone while driving.
In the January 2012 issue of the journal Epidemiology Richard Young, Ph.D., professor of research in Wayne State University's Department of Psychiatry and Behavioral Neurosciences in the School of Medicine, examined possible bias in a 1997 Canadian study and a 2005 Australian study - both of which were considered quite influential.
The earlier research used cellphone records of people who were involved in a crash and compared their cellphone use just before the crash to the same time period the day (or week) before - the control window.
The problem with the above-mentioned studies?
The subjects 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 Young.
"This false assumption makes it seem like cellphone conversation is a bigger crash risk than it really is."
Young’s new study employed Global Positioning Satellite (GPS) data to follow day-to-day driving of more than 400 drivers during a 100-day period. Young and his team then divided the days into pairs: the first day represented the "control" day, while the second day represented the "crash" day in the earlier studies.
Interestingly enough, the team found a lack of driving consistency in the given clock time periods between the two days. Essentially, driving time on the control day was only about one-fourth of the driving time on the crash day - during any specific clock time period.
"This underestimation of the amount of driving in the control windows by nearly four times could reduce cellphone conversation time in that control period," Young said.
"It makes it appear that there is less cellphone conversation in control periods than in the time just before a crash, making the relative risk estimate appear greater than it really is."
Young discovered that when the cellphone conversation time in the control window was appropriately adjusted, the amount of cellphone usage in the control window was almost the same as in the minutes before a crash. This led him to believe that the crash risk for cellphone conversation while driving is one-fourth of what was claimed in previous studies.
Young explained that many well-controlled studies with real driving show that the main increase in crash risk from handheld electronic devices is from tasks where drivers need to look at the device or operate it with their hands. This obviously includes texting while driving.
"Tasks that take a driver's eyes off the road or hands off the steering wheel are what increase crash risk," he explained.
"Texting, emailing, manual dialing and so forth - not conversation - are what increase the risk of crashes while driving."
The National Transportation Safety Board (NTSB) recently recommended that all 50 states and the District of Columbia ban the non-emergency use of portable electronic devices for all drivers. Young said this recommendation goes beyond the data from newer studies, including his, because it would ban cellphone conversations while driving.
"Recent real-world studies show that cellphone conversations do not increase crash risk beyond that of normal driving - it is the visual-manual tasks that take the eyes off the road and the hands off the wheel that are the real risk," said Young.