Naturalistic Census of Cell Phone Use

One hundred eight drivers participated in a naturalistic field operational test. Each participant drove an instrumented passenger car for 6 weeks. Video data from the first week of driving for each participant were visually scored for all instances of cell phone use. These instances were divided into cell phone calls (conversations) and cell phone interactions that were not calls (visual or manual tasks involving the cell phone). Researchers examined 1,382 conversations and 2,149 visual or manual tasks. Participants were engaged in cell phone conversations 6.7% of all driving time and in visual or manual tasks involving a cell phone 2.3% of all driving time. Overall, conversations had a mean duration of 2.6 min, and participants engaged in conversations at a rate of 1.5 conversations per hour. Younger drivers were significantly more likely to be engaged in either type of cell phone task than older drivers and significantly more likely to be engaged in visual or manual tasks than middle-aged drivers. Drivers were more likely to initiate conversations and visual or manual tasks when stopped than at higher speeds; this finding may suggest a level of self-regulation. Furthermore, the finding suggests that estimates of crash risk that are based on assumptions that behavior observed in stopped vehicles translates to behavior in moving vehicles is incorrect and will result in overestimates of driver engagement in cell phone use.