# Creating an Interactive Urban Traffic System for the Simulation of Different Traffic Scenarios
## 2 Virtual Reality in Urban Traffic Simulations  
The idea of simulating urban traffic systems, in the sense of \"traffic as a simulation of object\" [4], has a long tradition and has made regular advances with new technology and methods (see also [5]). Several research efforts have been made to apply technological and methodological innovations to simulate traffic situations, such as CAD and GIS [6; 7; 8], parallel computing [9], and 3D modelling [10; 11]. With increasing computing power, the number of objects has also increased within virtual traffic models cf. [12; 13; 14]. Approaches to the use of virtual reality began to play an increasingly important role in the 2010s (e.g., [15]).  
Today, VR technologies are known in geoinformation sciences for the development of immersive environments and have so far only been used sporadically for traffic simulation. To bring together traffic planning and the design of sustainable urban spaces, bike simulators that facilitate immersive VR have recently been developed [16; 17; 18]. With respect to inner-city automobile traffic, few studies are available to date that address specific components of VR-based simulations.  
[PERSON] et al. [19] discussed approaches to the dynamic visualization of 3D sound for VR-based road traffic simulations. Beyond the visualization of urban soundscape ecology, [PERSON] et al. [20] used 3D sound in immersive VR to study pedestrian decisions in intersection situations. Using deep learning approaches, [PERSON] and [PERSON] [21] attempted to analyze pedestrian and vehicle interactions in immersive VR. Currently, research on the technical development of interacting transportation systems in immersive VR is scarce. This study follows up on this by presenting an approach to an interacting traffic system in immersive VR.  
When it comes to traffic simulations within the game engine Unity, which became free to use in 2015 for personal users, there is a lack of publications dealing with the creation of transport systems from a non-expert developer perspective. [PERSON] and [PERSON] [22] created a workflow based on a combination of different proprietary and freely available stand-alone software to implement a traffic system into the game engine Unity. The use of proprietary software in this workflow might be a hurdle for developers who want to benefit from freely available software such as Unity and also implement a traffic system without the use of additional third-party software. [PERSON] et al. [23] used the freely available traffic simulation software SUMO to implement traffic into Unity, but focused on the analysis than the implementation and visualization of the traffic system. [PERSON] and [PERSON] [24] used a visual programming language to simulate random traffic and autonomous driving.  
Thus, in this paper, the proposed method provides a cost-effective solution to allow developers of immersive virtual environments without a technical background in traffic simulation to quickly add traffic to their immersive virtual environments in Unity, without the need to learn and use additional third-party (proprietary) software.