Behavioural adaptation to prototype level 3 automated driving systems on public roads

Behavioural adaptation refers to changes in user behaviour following the introduction of changes in the road-vehicle-user system. The introduction of automated driving systems (ADS) triggers changes in drivers’ perception, cognition, attitudes, performance, and the driver state as shown in a previous driving simulator study on repeated usage of an ADS (Metz et al., 2021). The present study aims at overcoming limitations associated with the driving simulator setup and replicates the study design on German public roads using prototype level 3 ADS. Three different versions of a level 3 ADS with different operational design domains (ODD) are compared in a between group design. N = 75 drivers experienced a level 3 ADS during four experimental driving sessions. The drivers were free to activate / deactivate the function as they liked and to spend driving time on self-chosen side tasks. With growing experience, the mental model of the system improves towards more realistic expectations towards system capabilities. At the same time, acceptance and perceived safety increase while stress decreases. Objective indicators of system handling are impacted by the ODD, however there are no changes with repeated usage. The results from the on-road study are compared with the results from the driving simulator and they are discussed with regard to the theory of behavioural adaptation.