The Role of NDRT Suspension in Facilitating Safe Control Transitions in Level 3 Automated Cars: Age- and Task-Dependent Insights

Abstract

Non-Driving-Related Task (NDRT) interruption has been proposed as a strategy to mitigate control-transition challenges in Level 3 cars. However, it remains unclear whether the system should actively suspend ongoing NDRTs. This paper presents the first study to test empirically whether suspending the NDRT at the moment of a Take-Over Request (TOR) improves takeover performance, hazard perception, and user acceptance across three age cohorts (22–32,60–69,70+) in Level 3 cars. Using a driving simulator, participants responded to TORs during high- or low- mental demand NDRTs, under suspension and non-suspension (active) conditions. Suspension consistently reduced reaction times, yet its benefits were uneven: the largest gains appeared in the 70+ and 22–32 groups. The 60–69 group showed limited benefit in both reaction time and hazard perception, suggesting they retained cognitive flexibility. Suspension increased perceived workload under the high-demand NDRT. These findings establish the benefits and limitations of NDRT suspension and call for adaptive TOR design in future vehicles.