Shut up and drive.

This research examined the effect of naturalistic, hands-free, cell phone conversation on driver’s lane-changing behavior. Thirty-six undergraduate psychology students drove six 9.2-mile scenarios, in a simulated highway environment, with three levels of traffic density. Participants were instructed only to obey the speed limit and to signal when making a lane change. These simple driving instructions allowed participants to freely vary driving behaviors such as following distance, speed, and lane-changing maneuvers. Results indicated that, when drivers conversed on the cell phone, they made fewer lane changes, had a lower overall mean speed, and a significant increase in travel time in the medium and high density driving conditions. Drivers on the cell phone were also much more likely to remain behind a slower moving lead vehicle than drivers in single-task condition. No effect of cell phone conversation on following distance was observed. Possible implications on traffic flow characteristics are discussed.