###### Abstract  
Intervention by First Responders (FRs) is essential in disaster response, and their preparation greatly benefits from continuous updates. However, the design of effective training experiences targeted to FRs can be very demanding from the viewpoint of a Training Provisioner (TP). Virtual Reality (VR) may have a key role to play in enhancing and facilitating this task. In fact, VR technology has already proven to be very helpful in the field of emergency training, as well as its use as a powerful design and mock-up tool in many other contexts. In this work, the application of VR as a mock-up tool supporting TPs in the arrangement and validation of a training experience, either real or virtual, is explored. In particular, a case study is considered concerning the training of an FR for hydro-geological risks. Within this context, the proposed approach is compared against dramaturgy prototyping, a method commonly used for the design of experiential courses. Results indicate that the adoption of a VR-based mock-up tool (VRMT) can provide TPs with good insights on the arrangement of the training and precious indications on how to actually map this information onto real-world exercises. training design; mock-up tool; virtual reality; dramaturgy prototyping; experiential courses; First Responders +
Footnote †: Publisher’s Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. double-check the risks to which construction workers could be exposed and to leverage this information for optimizing building design in order to minimize these risks. Despite these findings, the use of VR as a tool to support the design of training experiences has gone mostly unexplored. However, VR technology itself already plays a large role in this context, as simulation-based training is attracting a great deal of interest from both academia and industry [8; 9]. In fact, VR training systems are expanding beyond laboratory settings and are increasingly frequently integrated into traditional training programs [10]. This is especially the case for teaching users how to carry out activities that are mainly composed of procedural and practical tasks, including the use of special equipment and machinery, which typically benefit from _learning-by-doing_ and _hands-on_ training approaches [11; 12]. For instance, the VR-based framework presented in [13] allowed a crisis management team--including a policeman for traffic control, a fireman for dealing with the emergency and a medical doctor for rescuing injured subjects--to collaborate within a VE representing a critical site. The considered scenario, namely a rescue mission of an injured individual lying on the floor of a subway station platform that was on fire, requested each actor in the simulation to follow different procedures and use specific tools to accomplish their own task: the policeman was in charge of delimiting the dangerous area and putting up a cordon, the fireman had to operate a fire hose to extinguish the fire, and the medical doctor had to measure the individual's vital signs. Moreover, the sandbox nature of the medium enables trainees to experience possibly harmful and unusual situations in a safe and repeatable virtual setting [14; 15]. VR training systems have been proposed in the literature both for rare and high-risk scenarios [13; 16; 17], as well as for common and low-risk scenarios [18; 19]. Despite the benefits brought by the use of VR technologies for simulation-based training, some aspects regarding the design and validation process of these experiences are still under investigation, as confirmed by the increasing number of studies on this topic. For instance, the authors of [20] described an empirical study on the use of VR to gather requirements in the field of simulation and training. More specifically, a number of stakeholders (navy officials and physicians) and developers collaborated in a joint design process for the development of two training scenarios.