The use of heart rate in a driving simulator as an indicator of age-related differences in driver workload

The degree to which driving complexity affects cognitive performance remains an area of great interest. Older adults do not necessarily perform as well as younger adults on complex cognitive tasks alone or when combined with different driving environments. Since the next generation of older adults is expected to drive more frequently than previous cohorts, we conducted an experiment in which subjects were presented with cognitive performance tasks during simulated driving involving four levels of environmental complexity. We monitored a physiological index, heart rate, to assess task impact on workload capacity. A total of 18 active younger drivers (19-23 years old) and 17 older drivers (51-66 years old) completed different cognitive tasks including: a simulated cellular telephone conversation (easy task), two paragraphs from the Wechsler Memory Scale (easy task), segments of the Continuous Performance Task (hard task), and Multiple Interference Task (hard task). Driving performance was measured using a validated simulation protocol in a full cab fix based simulator running STISIM Drive™ and heart rate was measured using an Agilent A1 Patient Monitor. Our results indicate that older adults appear to have more difficulty acclimating to the simulated driving environment. Physiologically, older adults had higher heart rates at the start of the driving task that then declined only gradually over the course of simulation experience compared to younger drivers. The pattern of heart rate response also differed by age group with younger adults generally showing higher magnitude rate increases during the cognitive tasks. On the easy cognitive tasks younger and older adults performed equally well, while, younger drivers performed significantly better on the hard cognitive tasks. We conclude that collection of heart rate, a traditional physiological measure, provides additional insight into the differential workload impact on younger and older drivers.