  Understanding how trust is built over time is essential, as trust plays an
important role in the acceptance and adoption of automated vehicles (AVs). This
study aimed to investigate the effects of system performance and participants'
trust preconditions on dynamic situational trust during takeover transitions.
We evaluated the dynamic situational trust of 42 participants using both
self-reported and behavioral measures while watching 30 videos with takeover
scenarios. The study was a 3 by 2 mixed-subjects design, where the
within-subjects variable was the system performance (i.e., accuracy levels of
95\%, 80\%, and 70\%) and the between-subjects variable was the preconditions
of the participants' trust (i.e., overtrust and undertrust). Our results showed
that participants quickly adjusted their self-reported situational trust (SST)
levels which were consistent with different accuracy levels of system
performance in both trust preconditions. However, participants' behavioral
situational trust (BST) was affected by their trust preconditions across
different accuracy levels. For instance, the overtrust precondition
significantly increased the agreement fraction compared to the undertrust
precondition. The undertrust precondition significantly decreased the switch
fraction compared to the overtrust precondition. These results have important
implications for designing an in-vehicle trust calibration system for
conditional AVs.
