Weir, D., Chao, K., and Van Auken, R., "A Metric To Quantify Attentional Workload In Dual Task Driving Conditions," SAE Technical Paper 2017-01-1376, 2017, doi:10.4271/2017-01-1376.
A class of driver attentional workload metrics has been developed for possible application to the measuring and monitoring of attentional workload and level of distraction in actual driving, as well as in the evaluation and comparison of in-vehicle human machine interface (HMI or DVI) devices. The metrics include driver/vehicle response and performance measures, driver control activity, and driver control models and parameters. They are the result of a multidisciplinary, experimental and analytical effort, applying control theory, manual control, and human factors principles and practices. Driving simulator and over-the-road experiments were used to develop, confirm, and demonstrate the use of the metrics in distracted driving situations. The visual-manual secondary tasks used in the study included navigation destination entry, radio tuning, critical tracking task, and a generic touch screen entry task. Non-visual-manual secondary tasks included visual-voice navi, hands free cell phone, Sternberg surrogate task, and a conjunction search task. The metrics provide objective measures of the driver's attentional workload or level of distraction in a dual task situation. In addition to objective driver/vehicle performance measures, and unique to this study, driver describing function measures of driver gain and time delay were calculated on a continuous real time basis for steering control tasks. These describing function terms give a direct measure of the level of driver control activity and attention to the primary driving task. Novel methods were used to obtain the driver describing function measures continuously in real time in over-the-road conditions, using the basic response and performance measures already available in a typical vehicle. As objective metrics of distraction or attentional demand, the metrics can also be used to compare dual task workload against a baseline, or to compare two dual task situations and HMIs. The metrics are intended to quantify and monitor level of distraction in dual task conditions.