Automobiles and bicycles simultaneously traversing through a roundabout present a unique traffic problem. In such situations, it is imperative that the automobile drivers and bicycle riders recognize and anticipate one another throughout the intersection (inflow, outflow, and circular section). However, an appropriate method to ride a bicycle in a roundabout has not yet been established in Japan. Besides, there are no operating guidelines for driving automobiles in a roundabout despite the increasing number of roundabouts.
In this study, experiments for extracting evaluations from the viewpoints of an automobile and a bicycle were conducted using virtual reality (VR). The influence of the automobile and bicycle users on each other was examined quantitatively at the inflow, outflow, and circular sections of the roundabout. The following findings were obtained from the experiments:
1. When a bicycle is ridden in the leading area of the inflow section, the automobile driver behind the bicycle has a high sense of danger and discomfort.
2. When the automobile driver is in the inflowing area of the bicycle rider at the inflow section, the automobile driver has a high sense of danger and discomfort.
3. Automobile drivers and bicycle riders who enter the road at the inflow section have a low sense of danger and discomfort when they enter the roundabout alone.
4. Automobile drivers and bicycle riders have a high sense of danger and discomfort when they are immediately beside each other in the roadside section.
5. When driving/riding behind one another in the roadside section, automobile drivers/bicycle riders have a low sense of danger and discomfort.
6. When driving in the leading and trailing positions, the drivers and riders have a low sense of danger and discomfort.
7. When leaving at the outflow section, the first person to exit (either driver/rider) has a low sense of danger and discomfort.
From these findings, we draw the following conclusions:
1. When operating an automobile in a roundabout, the driver should not drive in the trailing region of a bicycle at the inflow section.
2. Automobile drivers should not drive immediately beside bicycles in the roadside section.
3. As the bicycle rider has a sense of danger or discomfort regarding the automobile at the outflow section, the automobile driver is required to consider the traffic-weaker. On the other hand, when riding a bicycle in the roundabout, the rider should not be in the leading area of an automobile at the inflow section.
4. Bicycle riders should not ride immediately beside automobiles in the roadside section. Bicycle riders are required to have a sufficient understanding of and anticipate the difference between the driver's awareness and the risk of traffic conditions at the outflow section.
