The importance of task duration and related measures in assessing the distraction potential of in-vehicle tasks

The issue of task duration in the assessment of driver distraction has been a controversial topic. In the development of J2364 Navigation and Route Guidance Function Accessibility While Driving, task duration and a related criterion were the most difficult parts of achieving consensus. The current discussion is restricted to a few key criticisms of task duration and duration-related measures of driving performance. We provide data-driven reasons why criticisms of duration-related measures, though important, are not sufficient to negate the value of these measures. Further, we point to naturalistic driving research that indicates it is glances away from the road scene prior to critical events that predominate in real-world crashes and near-misses. Rather than suggesting duration-related measures be abandoned, naturalistic driving research underscores the importance of using driver metrics like total eyes-off-road time as well as single glance durations. Finally, task length is an attribute of a task and HMI design, which can be modified through re-design and therefore will influence duration-related performance. We argue that duration is particularly important as a tool to assess where interventions to limit distraction might be applied.