There remains some debate regarding secondary task distractions, such as cell phones, as a risk factor in traffic crashes and their relative risk compared to existing factors, such as engagement in common in-vehicle tasks and alcohol impairment. Moreover, studies of driver impairment often investigate single risk factors rather than combined factors (e.g. distraction task while drunk). This study compared non-distracted driving in a motion-based driving simulator to distracted driving (hands-free cell phone conversations, common in-vehicle tasks) either while sober or combined with alcohol (BAC 0.08). The results indicated that during a car following scenario, drivers engaged in the conversations or completing in-vehicle tasks were more impaired than drivers that were not involved in any distraction task. Indeed, both the cell phone and in-vehicle sources of distraction were generally more impairing than intoxication at the legal limit.
