# Virtual Reality for Spatial Planning and Emergency Situations: Challenges and Solution Directions
## 1 Introduction  
Virtual reality (VR) is a technology that allows users to experience a sense of place that is comparable or even identical to the real world [1]. Although the first forms of VR date back to the 1960s, with later applications in building design in the 1970s [2], the modern head-mounted device that is accessible to the general public was only developed for widespread commercial uptake in the past decade [3], with the Quest Go being a particularly prominent factor in this realization [4]. An advantage of using VR over real-world experiments is the safe environment in which emergencies can be experienced by participants [5]. In addition, the costs for a VR experiment are relatively low in comparison to a real-world study, and a VR application can be used repeatedly, thus making the technology's uptake readily scalable and affordable [6]. Additionally, when compared to traditional 2D methods (i.e., maps and images), VR has been shown to improve a person's ability to recognize objects and to remember what they saw [7]. An advantage of using VR for smart city applications (e.g., for spatial planning and emergency situations) is that the technology can contribute to displaying extra layers of information on top of the original environment, in essence, bringing immersive experiences [8]. [PERSON] et al. [9] describe these layers of information as Data Layers (DL). Displaying these DLs improves communication and, therefore, the understanding of designs or existing places [9]. Following this concept of DL and information generated for smart city management, the concept of layers showing extra information and data together with the real environment will be referred to as smart city data layers (SCDLs) in this article. The notion of the smart city has gained prominence over the last 15 years. Yet, considering the twenty-three different definitions that have been found by [10], there is no single agreed-upon definition. However, what all definitions of a smart city have in common is the identification that Industry 4.0 technologies should be present and should improve the lives of the inhabitants [11]. To design a smart city, it is essential to have effective communication between clients, designers, communities and decision-makers [9]; thus, investigations of the integration of DLs are gaining prominence for spatial planning and emergency situations. However, for clarity, this communication does not necessarily need to be on the scale of a whole city but can also be localized to, for example, an individual building. This is because one of the critical components of a smart city is public safety [12]. At the building level, public safety can be increased by improving the individual's knowledge of emergency routes. During an evacuation, wayfinding skills are of great importance and can contribute to the chance of survival [13]. Specifically, there are five factors that influence wayfinding skills in buildings, namely, visual access, architectural differentiation, layout, familiarity and signage. While research on wayfinding and associated factors has traditionally been conducted through real-world experiments, modern visualization techniques, such as VR, have emerged as a viable alternative approach for research [14]. Existing research has shown that VR applications are able to improve wayfinding skills [15] and can be used both by persons visiting a building for the first time or by emergency responders. The technology has also demonstrated a positive impact, with the use of VR tools demonstrating increased chances of survival in emergencies. For example, [PERSON] and [PERSON] [16] developed a VR tool that contributes to public safety by studying pre-evacuation behavior. Besides escaping, users of this application can also choose to help others or extinguish a fire. [PERSON] et al. [17] also contributed to public safety by using VR to evaluate and improve emergency signage, which is one of the five factors that influence wayfinding skills in buildings.