The purpose of this study was to examine naturalistic driving data for evidence of a dose–response relationship between cell phone use and crash risk. The day-to-day driving behaviour of 105 participants was monitored for one year. The proportion of driving time spent using a cell phone was estimated for each 3-month period and then correlated with the overall crash and near-crash rates for each period.
Results revealed that participants spent approximately 11.7% of their driving time using their cell phone, whether it was talking on the phone (6.5%) or holding the phone in their hand or lap (3.7%). When drivers were talking on the phone, the risk of near-crash and crash events increased by 17%. Furthermore, the speed of the vehicle within the first six seconds of each cell phone call was 5-6 mph lower, on average, than speeds at other times.
Farmer, C. M., Klauer, S. G., McClafferty, J. A., & Guo, F. (2015). Relationship of near-crash/crash risk to time spent on a cell phone while driving. Traffic injury prevention, 16(8), 792-800.