Who’s the boss? Arbitrating control authority between a human driver and automation system

•Compared five driving modes in their ability to mitigate human and automation faults.•Sharing control with automation during driving improves the driving performance.•Ability to handle human faults is low when automation intervenes in manual driving.•Ability to handle automation faults is low when human intervenes in automatic driving.•Driving performance is better when the transitions of driving authority are gradual. Progress toward the fully automated highway will first require that manual and automatic control be successfully combined. Determining a combination that preserves the best performance features of human and automatic control yet allows either driver to cover for the faults of the other is a challenging problem. In this study, we invited 11 participants to drive a simulated vehicle through a course with obstacles to investigate the ability of human-automation teams to cover for human and automation faults. We developed the automation system using model predictive control and implemented three schemes under which the human would share control with the automation. In Autopilot, the human driver initiated a takeover with a button press whereas in Active Safety the automation initiated a takeover when it anticipated an obstacle collision. In Haptic Shared Control the human was free to invoke a transition by activating or relaxing muscles. In addition, we included two baseline conditions in which control was given in whole to either the human or the automation. We compared performance in the five conditions by analyzing obstacle hits and metrics related to driving maneuvers around the obstacles that were avoided. Relative to individual human or automatic driver performance, we found that control sharing reduced obstacle hits under fault conditions but also occasionally resulted in obstacle hits under no-fault conditions. Our findings further indicated that team performance suffered most under Autopilot for automation faults and suffered most under Active Safety for human faults. Haptic Shared Control supported the best overall team performance.