## 3 Methodology
### Driving Simulation  
It is necessary to establish a road network in which the vehicle can drive to perform a driving simulation. Road geometric characteristic information currently used in Korea's freeway crash database was used to select the representative road-alignment conditions  
Figure 5: Algorithmic description of obstacle avoidance [27]. Figure 6: Algorithmic description of merge [27]. for simulation experiments [1]. The criteria for categorizing the horizontal curve length and longitudinal slope of the freeway accident data are shown in Table 1. The horizontal curves in the freeway accident data are categorized based on 500 m and 1000 m. Uphill and downhill are categorized by 1% and 3%, respectively. A total of 24 road sections, including various alignment conditions, were prepared. The radius of the horizontal curve was set equally to 710 m in consideration of the minimum required design standard [28]. In addition, a flat tangent section was placed between each analysis section to minimize the influence of the adjacent road-alignment characteristics and to independently evaluate the driving safety in each section. The length of the tangent section was 250 m, which corresponded to the minimum stopping distance [28]. The total length of the network was 22.3 km, which consisted of a horizontal curve, vertical curve, combined alignment, and tangent section. The driving scenarios consist of three different car-following pairs. The scenarios include AV pairs, MV pairs, and mixed pairs. An AV pair is a case in which both the preceding vehicle and the following vehicle are AVs. An MV pair refers to a scenario where both the preceding vehicle and the following vehicle are MVs. Meanwhile, the mixed pair, which is the main concern of this study, is composed of \(\mathrm{AV_{L}}-\mathrm{MV_{F}}\) pairs and \(\mathrm{MV_{L}}-\mathrm{AV_{F}}\) pairs depending on the combination of AVs and MVs. The MV follows the AV in the \(\mathrm{AV_{L}}-\mathrm{MV_{F}}\) pair, but the AV follows the MV in the \(\mathrm{MV_{L}}-\mathrm{AV_{F}}\) pair. An experimental environment was constructed in which a multi-agent driving simulator was interlocked to enable simultaneous travel in the same space after the two driving simulators were synchronized using the network. Figure 7 illustrates the concept of the multi-agent driving simulation. Each simulator is connected via the TCP/IP communication protocol. Simulators send driving status data including the positions, speeds, accelerations, brake powers, and angular velocities. SCANeRTM STUDIO is used to construct a simulation environment by designing 3D virtual reality for road alignments and scenarios. This study conducts a car-following situation between preceding and subject vehicles using MADS. In the simulated environment, two drivers drive at the same time. The driving simulation environment is designed to drive two vehicles on a three-lane freeway. Drivers can increase the vehicle speed up to 100 km/h. During the driving simulation experiment, the drivers do not overtake the preceding vehicle. Additionally, both the preceding vehicle and subject vehicle drivers are instructed to keep driving in the second lane without lane changes. Drivers can determine their driving behavior in accordance with the surrounding vehicles or road alignments. Vehicle trajectory data are found using each simulator through which the preceding and subject vehicles have traveled the network. The driving behavior of individual vehicles and vehicle interactions are analyzed using the discovered trajectory data.