Measuring takeover performance in different driving scenarios: Considering the influence of non-driving-related tasks and takeover request lead time

Conditional automation systems (SAE Level 3) allow the driver to perform a secondary task, but the driver must regain control of the vehicle after the takeover request (ToR). Therefore, it is important to understand the factors that influence the driver's takeover performance. Previous studies have analyzed the variables including ToR modalities, ToR lead time, non-driving-related (NDR) task, driving experience and age. The influence of driving scenario on driver takeover performance and whether this influence varies the effect of the ToR time and NDR task remained unanswered. This study designed a 2(ToR time) x 2(NDR task) x 4 (driving scenario) factorial measure to investigate the effect of these factors on automated vehicle takeover performance. Forty-two participants drove in a simulated SAE Level 3 vehicle and performed a series of takeover tasks. The results showed that the ToR time, NDR task, driving scenario and ToR time x driving scenario had a significant effect on takeover behavior. In particular, the secondary work state task was correlated with the increased takeover and control time. The complexity of the driving scenario indicated a marginally significant influence on the quality of the takeover. A shorter takeover time and a smaller lateral offset were associated with a lower urgency of the driving scenario. The ToR time for the fog-cluster scenario showed an opposite effect to the takeover performance compared to the other three scenarios. Findings from this study can provide implications on the effect of ToR time desired and enabled by different scenarios.