The arrival of highly automated vehicles introduces a new interaction between the vehicle and driver. System limitations during highly automated driving require the driver to be ready to take back control at request. Previous studies on the take-over process concluded that the driver requires a transition period to stabilize vehicle control after resuming manual control. These studies used traded control to instantaneously transfer control back to the driver, causing an abrupt switch in control authority. This study explores Haptic Shared Control as a potential approach to mitigate these stabilization issues, and assist the driver to make a lane change. We expected that Haptic Shared Control improves the take-over performance compared to the traded control approach. A total of 30 participants drove two trials in a driving simulator, one for each transition approach. Each trial consisted of 10 takeover scenarios, where driver had to avoid a stationary car in the lane ahead. The take-over scenarios had either a time-to-collision (TTC) of 5 or 7 seconds. During autonomous driving the participants were engaged in a non-driving related task. The take-over performance was assessed based on safety margins, steering wheel input, and subjective measures. Results showed that with the HSC approach drivers adopted larger safety margins in longitudinal direction, but smaller margins in lateral direction. The HSC approach yielded lower steering wheel velocities. The subjective measures did not yield any significant differences. These results suggests that haptic shared control can assist the driver in stabilizing lateral vehicle control after resuming manual control. On the other hand, HSC seems to slightly hinder the driver to execute her/his preferred trajectory. Future research should focus on designing an adaptable human compatible reference in order to mitigate conflicts during take-over scenarios.
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