Effects of unreliable automation, non-driving related task, and takeover time budget on drivers' takeover performance and workload

The objective of this study was to assess the effects of unreliable automation, non-driving related tasks (NDRTs), and takeover time budget (TOTB) on drivers' takeover performance and cognitive workload when faced with critical incidents. Automated vehicles are expected to improve traffic safety. However, there are still some concerns about the effects of automation failures on driver performance and workload. Twenty-eight drivers participated in a driving simulation study. The findings suggested that drivers require at least 8 s of TOTB to safely take over the control of the vehicle. In addition, drivers exhibited safer takeover performance under the conditionally automated driving situation than negotiating the critical incident in the manual driving condition. The results of drivers' cognitive workload were inconclusive, which might be due to the individual and recall biases in subjective measures that could not capture subtle differences in workload during takeover requests. Practitioner Summary: A driving simulation study was conducted to assess the effect of unreliable automation, non-driving related tasks, and different takeover time budgets on drivers' performance and workload. The results can provide guidelines for vehicle manufacturers to improve the design of automated vehicles.