Stabilization Time after Mode Switch in Conditionally Automated Driving: Focusing on Drivers’ Cognitive Load and Visual Attention

The switch between automated and manual driving modes is currently an inevitable topic for automated vehicles. Understanding how long it takes drivers to stabilize physically and cognitively after the driving mode switch is important to maintain driving safety. Given that little attention has been paid to drivers’ stabilization time after the driving mode switch, this study focuses on drivers’ cognitive load and visual attention and aims to investigate drivers’ stabilization time after the driving mode switch. Twenty-eight participants drove in a high-fidelity driving simulator where they experienced mode switching from manual to automated and from automated to manual. Reaction time to the detection response task and on-road fixation durations were measured throughout the experiment to assess drivers’ cognitive load and visual attention. Results revealed that it took drivers 10 to 15 s to stabilize their cognitive load after taking over the manual control of the simulated vehicle, and 5 to 10 s to stabilize after relinquishing manual driving to the automated system. These findings indicate that drivers’ cognitive load and visual attention will fluctuate after driving mode switches and a buffer time should be provided to ensure driving safety. By exploring drivers’ cognitive load and visual attention after driving mode switches, this study offers valuable insights into the design of automated driving systems and helps to improve road safety. In developing automated driving systems, efforts should be made to identify an appropriate time window for drivers to perform stable driving performance and improve their in-vehicle experience.