Driving context and visual-manual phone tasks influence glance behavior in naturalistic driving

Journal article, 2014

Naturalistic driving studies show that drivers engaged in complex visual-manual tasks face an increased risk of a crash or near-crash. Tasks that require many glances and a high proportion of long glances away from the road are of special concern for safety. Driving context (e.g. turning maneuvers, presence of lead or oncoming vehicles, vehicle speed) may also influence drivers’ glance behavior during normal driving, since the drivers may have to estimate curvature and anticipate potential threats (e.g., lead vehicle braking). However, the effect of driving context on glance behavior during visual-manual tasks has not yet been thoroughly investigated in naturalistic driving. The extent to which drivers adapt their glance behavior to changes in the road environment during secondary tasks is likely to influence their ability to compensate for and respond to changes in the road environment. The present study investigated for the first time the effect of both driving context and visual-manual phone tasks (i.e., dialing, texting, reading) on drivers’ glance behavior in naturalistic driving. This study shows that drivers indeed spend more time looking at the road and have a lower proportion of long off-road glances in complex driving contexts such as when turning and when lead or oncoming vehicles are present, both in normal driving and while engaged in a visual-manual phone task. In particular, these findings are more pronounced during turning maneuvers and in the presence of oncoming vehicles than in the presence of lead vehicles. Interestingly, driving speed influenced off-road glance durations during the phone tasks, but not during normal driving. The results from this study highlight the need to take driving context into account when evaluating the influence of different secondary tasks, in-vehicle user interfaces and glance metrics on driving safety, including the risk of crash involvement. The finding that glance behavior is context-dependent in a naturalistic setting has further implications for distraction detection algorithms, driver support systems, and driver training. Finally, driving contexts should be matched when comparing glance behavior, while driving with and without secondary tasks.