Compensatory Behavior of Drivers When Conversing on a Cell Phone

Abstract

Experimental studies have found that driving degrades when the driver is conversing on a cell phone. Naturalistic driving studies (NDSs), however, have not found conversing on a cell phone to be associated with increased risk of a safety-critical event (SCE). NDSs have found commercial motor vehicle (CMV) drivers to be at decreased SCE risk when conversing on a hands-free cell phone. This study used naturalistic driving data sets to investigate whether driver adaptation took place when drivers of light vehicles and CMVs were conversing on a cell phone. Baseline epochs 30 s prior to cell phone calls were sampled. Drivers’ travel speeds, headways, inclinations to travel in the slowest lane, inclinations to change lanes, and lane-keeping performances were compared. There was no indication that drivers increased their longitudinal safety margins when conversing on a cell phone. Their headways to a lead vehicle did not differ despite CMV drivers significantly increasing their speeds by 4 km/h (2.5 mph) when conversing on a cell phone. However, CMV drivers changed lanes significantly less and light-vehicle drivers unintentionally departed their lanes significantly less when conversing on a handheld cell phone. Overall, the observed performance changes were not substantial. Given that drivers look forward more often when conversing on a cell phone, it is likely that the increased visual attention to the forward roadway may ultimately be why conversing on a cell phone has not been found to increase SCE risk.