## 4 System Verification with Full-Vehicle Simulation
### Simulation Conditions  
Intersection geometry is one of the key parameters in analyses focused on traffic safety at intersections. [PERSON] et al. [28] stated that intersection geometry and intersection type influence driver behaviour at unsignalized intersections. This study focuses on a typical intersection geometry in Japan as a representative case, as shown in Figure 10a,b. As shown in the figures, the target road is a flat, right-angled, urban intersection where there is no longitudinal slope. The traffic lights are assumed to be in green status in both directions (meaning the ego vehicle could turn right and oncoming vehicles could continue  
Figure 9: Geometric relationship between ego vehicle and darting-out object.  
straight ahead). The simulations were conducted in an environment where there were no channelizing islands or median strips, and only oncoming vehicles had a blind area.  
In the target intersection, an oncoming four-wheeled vehicle darted out from the blind area of another stopped oncoming four-wheeled vehicle that was waiting to turn right when the ego vehicle turned right. After accelerating to an initial velocity of 40 km/h, the driver of the ego vehicle entered the intersection without operating the gas pedal and brake pedal. Therefore, the driver only operated the steering wheel during the right turn, and the vehicle velocity was controlled only when the speed assist system intervened. As shown in Figure 11, the on-board sensor was mounted on the right front edge of the ego vehicle, with detection distance \(R_{sensor}=120\) m and FOV = 70\({}^{\circ}\).  
It is assumed in the simulation that the sensor is able to recognize a darting-out vehicle with no delay time when the entire body of the target vehicle becomes visible. The detailed requirements for on-board sensors to detect oncoming vehicles in the real world (e.g., detection distance and azimuth) are presented by [PERSON] et al. [29]. In order to fairly compare the collision avoidance performance among various simulation conditions, the paths of the ego vehicle and the oncoming vehicle were strictly fixed in all conditions in the simulation. And the darting-out object entered the intersection at a constant speed while maintaining the lateral distance from the occluding vehicle \(D_{obj\_lat}=1.2\) m, as shown in  
Figure 11: Definition of sensor detection range and FOV.  
Figure 10: Intersection right-turn scene using full-vehicle simulation. (**a**) Object darting-out scene; (**b**) geometry of the target intersection.  
To evaluate the effectiveness of the system in various darting-out conditions, two scenario parameters were varied repeatedly. The first parameter was the velocity of the darting-out object \(V_{obj}\) and the second was the offset position of the darting-out object \(D_{obj\_offset}\). Simulations were performed under 441 different conditions, varying \(V_{obj}\) from 30 to 50 km/h and \(D_{obj\_offset}\) from 0 to 40 m. As shown in Figure 12, \(D_{obj\_offset}\) = 0 m was the position in which the ego vehicle and object would collide if they did not change their initial velocities and take any avoidance actions. Therefore, the initial position of the darting-out object is set so that a collision or near-miss situation between the ego vehicle and the object at the intersection will occur if the ego vehicle does not brake. The collision risk avoidance performances of vehicles equipped with the PBS and AEBS, or with AEBS only, were evaluated by comparing the presence/absence of collisions as well as the distance to the closest point of approach (DCPA) between the ego vehicle and the darting-out object under each condition. The values of the various parameters are shown in Table 1. Then, the speed limit at the intersection was set at 50 km/h and \(V_{vir}\) was also set to the same value.