The objective of this study was to test the hypothesis that cell phone use while driving is somewhat risky compared with distraction-free driving, but that cell phone use may reduce activities that are even riskier. This test was conducted by documenting trends in cell phone use and other secondary behavior for a sample of 105 individual drivers over the course of one year.
Results indicated that participants spent 42% of their driving time engaged in at least one secondary activity. Other than cell phone use (33%), the most common secondary activities included interacting with a passenger (12%) and talking/singing/dancing to oneself (5%). Therefore, although using a cell phone can be distracting from the driving task, other secondary activities can be equally or more distracting. Further, increases in the amount of driving time spent talking on a cell phone were associated with decreases in time spent on other distracting behavior and decreases in eye glances not related to the driving task.
Farmer, C. M., Klauer, S. G., McClafferty, J. A., & Guo, F. (2015). Secondary behavior of drivers on cell phones. Traffic injury prevention, 16(8), 801-808.