# Goal Estimation of Mandatory Lane Changes Based on Interaction between Drivers
## 1 Introduction
This indicates the possibility of an accident when not considering the interaction between drivers. In [7], the game theory was applied  
Figure 1: Examples of lane changes: (**a**) the vehicle on the mainstream lane is slowing down and gives passage. Conversely, (**b**) the vehicle accelerates and rejects the lane-changing from the acceleration lane. for considering an interaction model at intersections. This model assesses an interaction between the lane-changing vehicle and vehicles on the target lane based on a time-to-collision (TTC). The interaction is defined as a reward, and the model decides according to the reward. A large value of TTC represents a safe condition compared to a small value. However, there is a problem that the TTC has a large value despite the insufficient distance between the two vehicles when the relative speed is small. It has been reported that the TTC cannot appropriately assess driving safety under some conditions [8; 9]. Consequently, a new index is required to assess the interaction with the surrounding vehicles. Considering the above situations, we propose a novel method to estimate the goal of MLC based on the interaction between drivers. The proposed method applies the dynamic characteristic potential method to evaluate the interaction [10]. Surrounding vehicles are defined as moving obstacles, and the distribution of potential field is determined according to the acceleration of the subject vehicle, relative speed, and distance with respect to surrounding vehicles. Then, the space which has the minimum repulsive energy is selected as the goal for lane-changing. This selection assumes that the high repulsive potential energy represents a high collision risk. After that, the collision risk while performing lane-changing is assessed based on the trajectory prediction. If the collision risk with vehicles on the mainstream lane exists during the lane-changing, it is decided that the subject vehicle would maintain the current lane until the collision risk is eliminated. Through the above process, the proposed method realizes the goal estimation and overcomes the limitation of previous methods. The following three points can be discussed as the contributions of this paper:  
* This paper proposes a novel approach to estimate the goal of lane-changing. To the best of our knowledge, there is no paper to handle the goal estimation since most previous studies have discussed only the possibility of lane-changing. * For considering the interaction between drivers, the dynamic potential field method is applied. The advantage of using the method is a description ability about discontinuous conditions. Since the potential field is continuously distributed on the lanes, it can prevent the unstable estimation, caused by using the relative distance or speed, even the corresponding vehicle changes a lane or overtakes other vehicles. * The proposed method guarantees the best performance even the previous method is applied to the goal estimation. By extracting the novel features and checking the collision risk based on the trajectory prediction, the great accuracy of goal estimation can be ensured. This paper is organized as follows. Section 2 describes the problem definition in this paper. Section 3 explains the details of the proposed method. Section 4 presents the experiments, results, and discussion. Finally, Section 5 describes the conclusions of this paper.