# Creating an Interactive Urban Traffic System for the Simulation of Different Traffic Scenarios
## 4 Discussion: Technical Limitations and Solutions  
Theoretically, the implementation and connection of the individual components of the asset should result in a functional urban traffic system that runs open-end without errors. However, issues have occurred in the development process of the traffic system that occasionally brought it to a complete breakdown, as shown for example in Figure 5. In this particular case, traffic accidents occurred in the areas of the starting waypoint routes used to load vehicles. This error occurred when two vehicles took different routes on turning  
Figure 4: Traffic light meshes attached to a 3D model of a traffic light VR intersection situation. points but reached the endpoints of the different waypoint routes at the same time, which also caused them to be loaded to their starting waypoint route at the same time. The cause of this error was that the vehicles were loaded to their starting waypoint routes at the same time. This caused these vehicles to collide with each other, fall over and become unable to drive, leading to a blockage of the road, which prevented other vehicles from continuing their route, since these crashed vehicles were recognized as obstacles. This highly relevant issue counteracting the idea of an open-end loop could not be handled by the opportunities of the asset itself. It required the customized implementation of an adjustment. To solve this issue, a collider was placed in the location of the waypoint routes used to load the vehicles. Additionally, blockades were placed at the ends of the waypoints. The collider at the loading waypoint routes is used to check whether there are currently any vehicles in the waypoint route area. If this is the case, the deployed collider at the end waypoint routes is activated and prevents vehicles from reaching the endpoint and being loaded to the starting point of their waypoint route. Other solutions to this error, such as disabling the vehicle colliders while on the starting waypoint route, are imaginable. Another issue is that by actively moving the avatar into the interaction through the user, a gridlock of the traffic system can be triggered because the avatar is set to be recognized by the vehicles as an obstacle and ensures that the vehicles stop. If the avatar is placed within the intersection in such a way that the vehicles stop and block each other, since the avatar is detected as an obstacle, this leads to a traffic gridlock situation as shown in Figure 6. Such a traffic gridlock would not resolve itself and would persist until the application is restarted. To resolve such gridlocks caused by irrational user behavior, vehicles that have not moved for a fixed time period are loaded back to their starting waypoint routes and disappear from their current position in the environment. The waiting time has been set longer than the stop time of the traffic light phase so that the vehicles waiting at the traffic lights are not mistakenly loaded to their starting waypoint routes. Considering that the vehicles disappear from the environment after the waiting time has expired, it could lead to a negative impact on the user's immersion if the disappearance is perceived. Figure 5: Traffic accident triggered by simultaneous loading of vehicles onto the waypoint route. There could be other difficulties in implementing a transportation system that is not encountered in the application example presented here. The traffic system implemented here did not consist of a closed system of waypoint routes, since the area of the virtual environment was limited to the intersection. Especially in the case of a further developed, more complex, and closed traffic network with more traffic volume, further sources of error and difficulties would be imaginable. Further developments in traffic systems should deal with the irrational behavior of users in order to avoid errors triggered by irrational behavior.