Driving context influences drivers\u27 decision to engage in visual-manual phone tasks: evidence from a naturalistic driving study

Abstract

Visual-manual phone tasks (i.e., texting, dialing, reading) are associated with anincreased crash risk. This study investigated how the driving context influences drivers\u27 decisions toengage in visual-manual phone tasks in naturalistic driving. Method: Video-recordings of 1432 car tripswere viewed to identify visual-manual phone tasks and passenger presence. Video, vehicle signals, andmap data were used to classify driving context (i.e., curvature, other vehicles) before and during thephone tasks (N=374). Vehicle signals (i.e., speed, yaw rate, forward radar) were available for alldriving. Results: The drivers were more likely to engage in phone tasks while standing still, and lesslikely while driving at high speeds or executing sharp turns, or when a passenger was present. Leadvehicle presence did not influence how likely drivers were to engage, but they adjusted their tasktiming to situations when the lead vehicle was increasing speed, resulting in increasing time headway.The drivers adjusted task timing until after making sharp turns and lane change maneuvers. Incontrast to previous driving simulator studies, there was no evidence of drivers reducing speed as aconsequence of phone task engagement. Conclusions: The results show that experienced drivers areskilled at using information about current and upcoming driving context to decide when to safelyengage in visual-manual phone tasks. However, drivers may fail to sufficiently increase safety marginsto allow time to respond to possible unpredictable events (e.g., lead vehicle braking). PracticalApplications: Advanced driver assistance systems should facilitate and possibly boost drivers\u27 selfregulatingbehavior. For instance, they might recognize when appropriate adaptive behavior is missingand advice or alert accordingly. The results from this study could also inspire training programs fornovice drivers, or locally classify roads in terms of the risk associated with secondary task engagementwhile driving