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Objective The aim of this study was to explore individual differences in voluntary and involuntary driver-distraction engagement. Background Distractions may stem from intentional engagement in secondary tasks (voluntary) or failing to suppress non-driving-related stimuli or information (involuntary). A wealth of literature has examined voluntary distraction; involuntary distraction is not particularly well understood. Individual factors, such as age, are known to play a role in how drivers engage in distractions. However, it is unclear which individual factors are associated with voluntary- versus involuntary-distraction engagement and whether there is a relation between how drivers engage in these two distraction types. Method Thirty-six participants, ages 25 to 39, drove in a simulator under three conditions: voluntary distraction with a self-paced visual-manual task on a secondary display, involuntary distraction with abrupt onset of irrelevant visual-audio stimuli on the secondary display, and no distraction. Results The number of glances toward the secondary display under voluntary distraction was not correlated to that under involuntary distraction. The former was associated with gender, age, annual mileage, and self-reported distraction engagement; such associations were not observed for the latter. Accelerator release time in response to lead-vehicle braking was delayed similarly under both conditions. Conclusion Propensity to engage in voluntary distractions appears to be not related to the inability of suppressing involuntary distractions. Further, voluntary and involuntary distraction both affect braking response. These findings have implications for design of in-vehicle technologies, which may be sources of both distraction types.

Driver distraction research primarily focuses on voluntary distraction. Little known research explicitly evaluates driver susceptibility to involuntary distractions. This paper investigates the relationships between glance behavior in response to irrelevant stimuli in a driving simulator and measures of inhibitory control assessed through a modified flanker task. Overall, inhibitory control appears to be a mechanism that relates to number of glances and average glance duration. Data from 16 participants show that smaller flanker compatibility effects (i.e., better inhibitory control) are significantly associated with fewer glances and shorter average glance durations to irrelevant stimuli in the simulator. No significant relation was found between time fixation on the irrelevant stimulus after its onset and the size of the flanker compatibility effect.

Smartwatches and other wearables are being developed for the consumer market and will most likely be used by drivers, but there is little investigation into their influence on driver behaviour. Smartwatches are able to provide certain smartphone functionalities. For example, they can provide notifications, such as text messages. Because watches are always "on-hand", drivers may find it easier and be more compelled to interact with them in comparison to smartphones. We conducted an exploratory driving simulator study to compare a smartwatch and a smartphone in terms of time to engagement with the device and drivers' glance patterns. The results show that participants (n=6) chose to engage with the smartwatch faster than with the smartphone, but took longer to read notifications. The smartwatch also led to a larger number of glances greater than 2 seconds than the smartphone. Further investigation of the effects on driving performance is required.