Assessing the effects of auditory-vocal distraction on driving performance and physiological measures using a driving simulator

In this research, a driving simulator experiment with physiological sensors is conducted to quantify the effect of an increase in workload on driving performance and physiological state in the presence of particular road situations. A secondary cognitive task with multiple levels of difficulty designed to simulate auditory-vocal distraction is added to the primary driving task. Driving performance and physiological indices such as heart rate and skin conductance level are monitored throughout the experiment. Nonparametric statistical tests are used to test the effect of the secondary task at three different road situations frequently encountered in an urban context. It is hypothesized that an increase in workload leads to variations in the driver’s physiology as well as decrement in his/her driving performance. Results of the study showed that the driver adopts a regulatory behavior at the operational level (e.g., reduces the speed) in order to allow the performance of the additional task and driving at the same time. The effect of the regulatory behavior is minor on the longitudinal and lateral control measures (e.g., the speed, the pedal depression, the lane position). However, the impact on the reaction time can have important implications for road safety. An increase in the heart rate and skin conductance level reflects the increase in the cognitive workload when performing the secondary task. No major differences are found in terms of the driving performance and the physiological measures across the difficulty levels of the secondary task at the three considered road situations. In order to maintain control of driving, particularly at the high levels of difficulty, some subjects are found to pay less attention to the secondary task and shift their focus towards the primary driving task. The study highlights the advantage of implementing the driver’s cognitive workload measures in the development, design, and assessment of effective in-vehicle safety systems.