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This paper presents the results of a study of how people interacted with a production voice-command based interface while driving on public roadways. Tasks included phone contact calling, full address destination entry, and point-of-interest (POI) selection. Baseline driving and driving while engaging in multiple-levels of an auditory-vocal cognitive reference task and manual radio tuning were used as comparison points. Measures included self-reported workload, task performance, physiological arousal, glance behavior, and vehicle control for an analysis sample of 48 participants (gender balanced across ages 21-68). Task analysis and glance measures confirm earlier findings that voice-command interfaces do not always allow the driver to keep their hands on the wheel and eyes on the road, as some assume.

Driving behaviors change over the lifespan, and some of these changes influence how a driver allocates visual attention. The present study examined the allocation of glances during single-task (just driving) and dual-task highway driving (concurrently tuning the radio using either visual-manual or auditory-vocal controls). Results indicate that older drivers maintained significantly longer single glance durations across tasks compared to younger drivers. Compared to just driving, visual-manual radio tuning was associated with longer single glance durations for both age groups. Off-road glances were subcategorized as glances to the instrument cluster and mirrors (“situationally-relevant”), “center stack”, and “other”. During baseline driving, older drivers spent more time glancing to situationally-relevant targets. During both radio tuning task periods, in both age groups, the majority of glances were made to the center stack (the radio display).