Driver takeover performance in conditionally automated driving: sudden system failure situation versus ODD exit situation

Conditionally automated driving is expected to become available to the public in near future. However, the driver is expected to take over control from the system when a sudden system failure occurs or when the driving automation system is approaching its operational design domain (ODD) exit. The time budget for drivers to take over control is different: (1) in the sudden system failure situation, the system needs to be deactivated immediately with issuing a request to intervene (RTI); (2) in the ODD exit situation, the system could keep active for a while after the issue of RTI. In this paper, two hypotheses were put forward based on driver’s expected utility analysis: (1) the drivers respond faster to the RTI in the system failure situation; (2) the drivers perform smoother driving behaviour after takeover in the ODD exit situation. We recruited 32 participants to conduct a driving simulator experiment, in which the driver takeover performance in system failure situation was compared with that in the ODD exit condition. Results revealed that drivers responded significantly faster in the system failure situation. There was no significant difference of longitudinal takeover performance between the two types of limitations. However, the drivers generally performed smoother lateral takeover performance in the ODD exit situation, which supported our hypothesis.