Young, R., "Self-Regulation Minimizes Crash Risk from Attentional Effects of Cognitive Load during Auditory-Vocal Tasks," SAE Int. J. Trans. Safety 2(1):67-85, 2014, doi:10.4271/2014-01-0448.
This study reanalyzes the data from a recent experimental report from the University of Utah investigating the effect on driving performance of auditory-vocal secondary tasks (such as cell phone and passenger conversations, speech-to-text, and a complex artificial cognitive task). The current objective is to estimate the relative risk of crashes associated with such auditory-vocal tasks. Contrary to the Utah study's assumption of an increase in crash risk from the attentional effects of cognitive load, a deeper analysis of the Utah data shows that driver self-regulation provides an effective countermeasure that offsets possible increases in crash risk. For example, drivers self-regulated their following distances to compensate for the slight increases in brake response time while performing auditory-vocal tasks. This new finding is supported by naturalistic driving data showing that cell phone conversation does not increase crash risk above that of normal baseline driving. The Utah data are next compared to those from a larger study that included visual-manual as well as auditory-vocal tasks. The Utah auditory-vocal tasks had negligible effects on response time compared to visual-manual tasks with socially acceptable crash risk, such as manual radio tuning. In conclusion, auditory-vocal tasks such as those in the Utah study are not expected to increase crash risk or impair real-world operation of an automobile, compared to normal baseline driving without performing such tasks.