Designing Two-Stage Warning Systems: The Effect of Hazard Information

Warning system design is critical to road safety in the automated driving takeover process. Two-stage warning system had been proposed to be an optimal solution to achieve better takeover performance. However, the two-stage warning system design needs further verification and validation. The primary purpose of this study is to explore the effect of warning content on takeover performance during the automated driving takeover process with a two-stage warning system design. Trust evaluations for the warning systems were also examined to validate the user experience with the alarm design. A within-subject design was used in this study. The within-subject factor was the warning content related to hazard information with two levels: warning with content and warning without content. A driving simulation experiment was conducted, and 32 participants (16 males, 16 females) drove two sessions with the two kinds of warning system design. The results showed that providing warning content to the TOR stage in the two-stage warning system design could result in slower reaction time and shorter TTCwpll. With or without warning content design did not influence drivers' trust evaluation for the two-stage warning system. This finding suggested that warning content should not be provided to the TOR stage when designing the two-stage warning system, which may result in traffic incidents due to an untimely takeover. This study helps design takeover warning systems.