  In this paper, a human-machine adaptive shared control method is proposed for
automated vehicles (AVs) under automation performance degradation. First, a
novel risk assessment module is proposed to monitor driving behavior and
evaluate automation performance degradation for AVs. Then, an adaptive control
authority allocation module is developed. In the event of any performance
degradation detection, the allocated control authority of the automation system
is decreased based on the assessed risk to reduce the potential risk of vehicle
motion. Consequently, the control authority allocated to the human driver is
adaptively increased and thus requires more driver engagement in the control
loop to compensate for the automation degradation and ensure AV safety.
Experimental validation is conducted under different driving scenarios. The
testing results show that the proposed approach is able to effectively
compensate for the performance degradation of vehicle automation through the
human-machine adaptive shared control, ensuring the safety of automated driving
