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). However, compared to visual-manual task periods, during the auditory-vocal periods, significantly more glances were made to situationally-relevant targets and fewer glances to the radio display. These results suggest that, while the auditory-vocal interface pulls some resources away from the forward roadway, it produces glance allocation profiles more similar to baseline driving. As with single-task driving, during the auditory-vocal radio task, older drivers made significantly longer glances off-road (173ms longer, on average), than younger drivers. These findings suggest that the assessment of glance behavior during on-road driving should consider that not all glances away from the forward roadway are necessarily “off-road”, i.e. diversions from driving-related attention.