An Experimental Study on the Difference in Drivers’ Decision-making Behavior During Manual and Supported Driving

The purpose of this study is to identify differences in characteristics of drivers’ decision-making when driving a vehicle with manual operation or with an automatic driving assistance system by using a high fidelity driving simulator. We controlled three experimental factors. The first is driving mode as a between-participant factor: manual driving and using automatic driving systems. The automatic driving system controls the vehicle's speed while recognizing peripheral vehicles. Moreover, it controls the steering when it is necessary to change the lanes and overtake slower traffic. The participants were also instructed to intervene with the steering and pedals and bring the vehicle to safety if they felt danger. They were required to drive for a total of 40 minutes for each condition. The remaining two are within-participant factors: relative speed between lanes and distance of destination. These two factors relate to experiencing risk. The experimental results are summarized as follows. First, in the automatic driving condition, the participants tend to avoid the lane changes compared with the manual driving condition. Second, the tendency to avoid lane changes correlates with reduction of risk sensitivity. These results show that while decisions to change lanes when using driving assistance systems were more careful, the sensitivity to risk situations might be reduced.