Effect of Similar Cognitive Secondary Tasks Under Different Levels on Takeover Performance within Various Time Windows for Transition Control from Automated to Manual Driving

Drivers will be required to maintain readiness to take over manual control of the automated vehicle occasionally during the highly automated driving until the advent of fully vehicle automation. Users can engage in cognitive tasks in this level of automated driving. However, it is unclear whether the engagement in cognitive secondary activities would impair or increase the driver's capacity to take over control authority. To explore such issue, four highly automated takeover scenarios were designed to study the individual and interaction effects of secondary tasks and time windows on takeover performance. Thirty participants engaged in similar cognitive tasks under different levels. A control group did not conduct any secondary tasks. Drivers had to resume vehicle control in four different scenarios while engaging in secondary tasks. The transition situation happened when a broken-down vehicle suddenly appears in front of the ego vehicle. Results show that there is significant difference in brake force, lateral offset and pitch, and no significant difference in sideslip angle-0 left, gas pedal, yaw speed and roll speed under different cognitive tasks. The takeover time under the condition of 0-back cognitive task is higher than that of no task (control group) and other two tasks, indicating that the proper workload of secondary task enhance alertness compared with the no-task, and high workload of secondary task could increase reaction time of takeover. The interaction effect between secondary task and time window on acceleration and brake force is not obvious. The significant difference exists in both individual and interaction effect of secondary task and time window on lateral offset and pitch. The findings could potentially provide reference for the design of safe and efficient highly automated driving systems during transition process.