Purpose: This study investigated the effects of visual and auditory secondary tasks on the driving performance of young and old participants with simulated visual impairment and those experiencing age-related declines in visual attention. Methods: Twenty eight participants comprising two age groups (younger, M=27.3 years; older M=69.2 years) drove around a closed road circuit under both single and dual task conditions. Measures of driving performance included detection and identification of road signs, detection and avoidance of large low contrast road hazards, gap judgment, lane keeping and time to complete the course. Performance was assessed for two levels of visual impairment compared to a baseline condition. Visual impairment was simulated using goggles designed to replicate the effects of cataracts and blur; all participants had binocular visual acuity greater than 6/12 when wearing the goggles and satisfied the visual requirements for driving. The secondary task required participants to verbally report the sums of pairs of numbers presented either through a computer speaker (auditorally) using computer-generated files or via a dashboard mounted monitor (visually) while driving. Results: Visual impairment significantly reduced driving performance (p<0.05) and these differences were greatest for the cataract condition. Multi-tasking further exacerbated the effects of visual impairment, where the visual dual task had a greater detrimental effect on driving performance than the auditory dual task (p<0.05), particularly for the older drivers. Conclusions: Multi-tasking (for example, talking on a mobile phone or using in-vehicle navigational devices) had a significant detrimental impact upon driving performance and these effects were exacerbated for older drivers and for those with simulated visual impairment. The implications of these findings are far reaching in modern society where the driving and in-vehicle environments are becoming increasingly complex and the elderly comprise the fastest growing segment of the driving population.