## 3 Experiments and Discussion
### Typical Collision Avoidance Scenes  
A typical collision avoidance scene on a straight road is shown in Figure 17. The first row shows the real scene, and the second row shows the path planning result of the autonomous vehicle during the collision avoidance. As shown in Figure 17a, the autonomous vehicle is keeping its lane, and three vehicles are detected. The left top vehicle is performing a left lane change, and two vehicles are moving along their lanes. In Figure 17b, a new vehicle is detected, which is taking a right lane change. The trajectory of the white car is predicted with the intent-estimation- and motion-model-based method, and a potential collision between the vehicle and the autonomous vehicle is detected, which is marked with a red circle. Then, a deceleration is executed, and a right lane change path is generated to avoid the collision.  
Figure 16: Maximum acceleration during collision avoidance.  
Figure 17: Collision avoidance on a straight road. (**a**) Keep lane without collision point detected; (**b**) collision point is detected and represented with a red point; (**c**) a lane change path is generated to avoid the potential collision. Trajectories of detected vehicles are represented by yellow lines and the planned path of the autonomous vehicle is represented by a green line. The red numbers represent the sequence number of the processed data from sensors and the internal between two frames is 40 ms.  
Figure 18 shows typical collision avoidance scenes when the autonomous vehicle is moving on a winding road. The detected vehicle is marked with a red rectangle, and its sequence number is 123. In the first picture, the driving intent of the vehicle, i.e., a right lane change, is inferred, and a collision point is obtained. Then, a deceleration is performed by the autonomous vehicle to avoid a potential collision. The distance between the autonomous vehicle and the front vehicle decreased first from 23 m to 16 m and then remained greater than 16 m in the following scenes. The maximum acceleration is 2.5 m/s\({}^{2}\).  
Figure 19 shows a typical collision avoidance process when applying the collision method used in [8], which ignores the driving intent of the detected vehicle. The detected vehicle is marked with red points, which are circled by a yellow rectangle. The velocity and moving direction of the detected vehicle, as well as the planned path of the autonomous vehicle are marked in red. The green box represents the dynamic obstacle detection range of the three-dimensional LIDAR, and the area between the two green lines illustrates the detection area of the IBEO LIDAR. A collision point was not detected until the detected vehicle entered the target lane as shown in Figure 18b. A lane change is simultaneously performed by the autonomous vehicle to avoid the potential collision. The collision point was detected too late, which resulted in a distance of 7.9 m between the autonomous vehicle and the detected vehicle.  
Figure 18: Collision avoidance on a winding road. (**a**) A collision point is detected; (**b**) decelerate to avoid the collision; (**c**) avoid potential collision successfully. The red number represents the ID of the detected obstacle which is unique.