Epidemiological studies of auto accidents have suggested that cell phone usage quadruples the risk of getting involved in a crash. Up might think that all conversations should be equally distracting, but this isn't the case -- passengers may actually improve the performance of the people driving them about. A new study examines the reasons for this.
There are at least three aspects of driving that appear to be negatively impacted by cell phone use. First, drivers on cell phones have a pronounced tendency to drift out of their lane. Second, it becomes more difficult to adjust to the cars around you on the road. Finally, drivers engaged in cell phone conversations are bad at strategic or task-focused processes, such as actually getting to their intended destination.
The new study used a highly sophisticated driving system called PatrolSim that's designed for training police officers. The tests were run on a simulated freeway, where the participants had to exit to a rest area. For live conversation, the authors recruited pairs of friends and asked them to discuss a "close call" situation, where one of them narrowly averted a life-threatening situation.
The study’s authors noted that compared to having a passenger, cell phone use made drivers' lane discipline worse, and doubled the rate at which drivers missed the intended exit. When the authors examined the conversation videos, some reasons for this difference became clear. Passengers frequently turned the conversation towards a discussion of traffic conditions and often noted when the relevant exit sign appeared. When a passenger was present, the pace of conversation also dropped as traffic increased, and participants often started using less complex language.