Publication

To explore driver behavior in highly automated vehicles (AVs), independent researchers are mainly using driving simulators and conducting short experiments. This limits the ability to explore drivers’ behavioral changes over time, which is crucial in the context of control transfer between drivers and AVs.

The project focused on a method development experiment that combines quantitative and qualitative data to capture effects of repeated interaction between drivers and AVs. Each driver (n=8) participated in the experiment on two different occasions (á 90 minutes) with one-week interval. On both occasions, the drivers traveled approximately 40 km on a rural road and encountered various traffic situations. They could engage automation or choose to drive manually. When activated, the automation was able to handle all situations on the road without requiring the driver to be engaged in maneuvering or monitoring (corresponding to SAE level 4). Examples of data collected include: vehicle state, driver biometrics, eye behavior, self-reported feeling of safety, as well as interviews and questionnaires capturing general impressions, trust and acceptance. The study was conducted at the AstaZero proving grounds in Sweden by Research Institutes of Sweden (RISE), Volvo Cars and Smart Eye.

The preliminary analysis shows that the first encounter effects were attenuated over time. The drivers went from being exhilarated ("fun", "cool", "impressive") on the first occasion, to a more neutral state ("positive", "safe", "good", "relaxed") on the second occasion. Furthermore, there were smaller variations in drivers’ self-assessed perceived safety at the second occasion, and drivers were faster to engage in non-driving related activities and become relaxed (e.g., they spent more time glancing off road and could focus more on non-driving related activities such as reading). These findings suggest that exposing drivers to AVs on two successive occasions may give more informative and realistic insights into driver behavior and experience as compared to only one occasion.

This study generated in-depth insights into behavioral changes of a limited number of drivers, however, these insights are difficult to generalize to a larger sample. Furthermore, the study was carried out during a winter period with varying adverse weather and road conditions, which may have affected driver behavior and embedded a bias in the findings. Our recommendation is that future studies of this type should be carried out under good weather and road conditions. Despite these challenges, the study generated knowledge on pros and cons with various data collection methods, something that is valuable for future studies.

The project was funded by SAFER Open Research at AstaZero, the Strategic Vehicle Research and Innovation (FFI) and the Knowledge Foundation (KK-stiftelsen).