Assertive Takeover Requests: Immediate and Sustained Effects on Stress and Performance

In conditionally automated driving, assertive takeover requests (TORs) have been found to elicit faster responses in the transition from automated to manual control. However, despite this apparent benefit, concerns have been raised that assertive signals can stress the drivers, resulting in worse takeover quality and subsequent driving performance.
To investigate the phenomenon, we conducted a driving simulator study exploring the effects of assertive and non-assertive TOR signals. In a series of tasks where the drivers were required to take over control of the vehicle to manually maneuver a critical situation, immediate and sustained measures of driving performance, stress, and subjective perceptions were compared.
Consistent with previous research, the assertive signal led to shorter reaction times and stronger braking. However, no other immediate or delayed differences in the measures were observed. These findings suggest that assertive TOR signals might be a preferable design option, however, the phenomenon should be further explored.