Abstract
Conditional automated driving [level 3, Society of Automotive Engineers (SAE)] requires drivers to take over the vehicle when an automated system’s failure occurs or is about to leave its operational design domain. Two-stage warning systems, which warn drivers in two steps, can be a promising method to guide drivers in preparing for the takeover. However, the proper time intervals of two-stage warning systems that allow drivers with different personalities to prepare for the takeover remain unclear. This study explored the optimal time intervals of two-stage warning systems with insights into the drivers’ neuroticism personality. A total of 32 drivers were distributed into two groups according to their self-ratings in neuroticism (high vs. low). Each driver experienced takeover under the two-stage warning systems with four time intervals (i.e., 3, 5, 7, and 9 s). The takeover performance (i.e., hands-on-steering-wheel time, takeover time, and maximum resulting acceleration) and subjective opinions (i.e., appropriateness and usefulness) for time intervals and situation awareness (SA) were recorded. The results showed that drivers in the 5-s time interval had the best takeover preparation (fast hands-on steering wheel responses and sufficient SA). Furthermore, both the 5- and 7-s time intervals resulted in more rapid takeover reactions and were rated more appropriate and useful than the 3- and 9-s time intervals. In terms of personality, drivers with high neuroticism tended to take over immediately after receiving takeover messages, at the cost of SA deficiency. In contrast, drivers with low neuroticism responded safely by judging whether they gained enough SA. We concluded that the 5-s time interval was optimal for drivers in two-stage takeover warning systems. When considering personality, drivers with low neuroticism had no strict requirements for time intervals. However, the extended time intervals were favorable for drivers with high neuroticism in developing SA. The present findings have reference implications for designers and engineers to set the time intervals of two-stage warning systems according to the neuroticism personality of drivers.
Highlights
With the rapid development of automated technologies, future road driving will be largely reformed
The present study conducted a driving-simulated experiment to investigate the effect of time intervals of two-stage warning systems and neuroticism personality on the takeover process
The mean and standard errors (SEs) of all dependent variables for time intervals and neuroticism are listed in Tables 2, 3, respectively
Summary
With the rapid development of automated technologies, future road driving will be largely reformed. Automated driving has several bottlenecks to overcome, it can reduce crashes, prevent deaths and injuries, and alleviate traffic issues, such as congestion and emission (Anderson et al, 2014). The available automated driving (i.e., conditional automated driving, level 3; SAE International, 2018) no longer requires drivers to supervise the traffic environment. It allows them to engage in various nondriving-related tasks (NDRTs) during the automation. The takeover process, which requires drivers to transfer from various NDRTs to driving tasks within a certain lead time, is of great importance for driving safety in level 3 (Society of Automotive Engineers, SAE) automated driving (McDonald et al, 2019)
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