Virtual Reality Evacuation Experiments on Way-Finding Systems for the Future Circular Collider

The European Organization for Nuclear Research (CERN) has been performing a feasibility study concerning the construction of the Future Circular Collider (FCC) on the border between France and Switzerland. The FCC would be a circular accelerator that would increase in a tenfold the current collision energy of the Large Hadron Collider (LHC) [1, 2]. The perimeter of the accelerator is expected to be between 80 km and 100 km long, excavated between 300 and 600 m underground [3]. This information concerning the geometric layout of the FCC makes it easier to understand that such a type of facility presents unique challenges from evacuation perspective [4]. In particular, the presence of very long and deep underground tunnels may lead to distances between emergency exits/protected areas that may exceed the distances adopted in standard road/rail tunnels (e.g. distances in American and European codes [5, 6]).

During a tunnel fire emergency, it is of crucial importance that evacuees take the appropriate actions in a timely manner [7]. In particular, the key decision to be taken in long underground tunnel accelerators is the direction of evacuation in the section that are not directly exposed to the threat (e.g. fire and smoke). The adoption of the wrong direction may lead people towards the fire threat, having possible negative consequences on human health due to the presence of smoke, heat and radiation [8]. In this context, way-finding systems are a useful technical solution to increase evacuees’ level of safety by guiding them towards appropriate routes and exits [9]. This is subsequently associated with a lower probability of exposure to hazardous conditions.

The fire safety and evacuation literature has proposed and investigated the usage of different way-finding installations and systems for road and rail tunnels, intended as any means able to provide information to the evacuees on the correct route to adopt [10]. Way-finding systems have been proposed for both smoke-filled [11‐13] and smoke-free environments [14], but their use and effectiveness has been tested mostly in accordance to current road/rail tunnel regulations, which generally advise for maximum distances between emergency exits/protected areas in the order of 300 m to 500 m [5, 6]. General guidelines exist concerning signage in tunnel, e.g. the use of ISO signs and symbols to provide safety information [15]. Given their unique configurations, particle accelerator tunnels may present longer distances between emergency exits/protected areas. They also require a safety standard which may be higher than other tunnel infrastructures, as there are potential risks associated with hazards that are uncommon in transportation tunnels (e.g. oxygen deficiency hazard associated to helium release scenario, etc.). For this reason, a necessary step for the feasibility study of the FCC design is the identification and evaluation of a set of the most advanced way-finding installations available today. The selection of the way-finding systems to be considered was made in accordance with three criteria (1) systems currently used at CERN in existing tunnel accelerators (2), the feasibility of implementation of new evacuation installations in the suggested FCC tunnel design, (3) the potential effectiveness of new systems. This includes the use of flashing lights [14, 16] and dynamic signage (such as dissuasive [17] and active signage [18]). A further innovative way-finding installation investigated here that could potentially be implemented in such type of facility is a robot on a monorail which includes an intelligent device to locate evacuees (e.g. such devices may be based on radiofrequency identification (RFID) sensors [19, 20] or thermal cameras [21]) and then provide way-guidance information. Those technologies may already be implemented in particle accelerator tunnel facilities for other scopes (e.g. identification of people location, maintenance [22], etc.) or infrastructures which requires a higher level of safety (e.g. mines [19]), thus their use for safe evacuation is feasible.

To address the issues associated with the fire safety design of the FCC, CERN has initiated a collaboration with a set of international institutions (particle physics accelerator facilities and academic institutions) to share knowledge and perform joint research on the fire safety design of FCC. Specifically, one part of the collaboration relates to the evacuation-related aspects of the fire safety design [23]. The aim of this work was the identification and evaluation of different evacuation design solutions for the FCC; these may include different fire safety-related technical installations.

This paper presents the results concerning possibly suitable evacuation design concepts which have been identified and compared for the deep and long sections of the accelerator tunnel. In particular, the main aim of this study is the investigation of the effectiveness of different systems aiming at providing way-finding information to evacuees in case of fire emergencies. The study has been performed with test participants which resemble the population that may be in an underground tunnel accelerator facility. The objectives of the work are therefore (1) the assessment of the suitability of a set of proposed evacuation design solutions including way-finding systems for the FCC accelerator tunnels, (2) the comparison of the performance of different evacuation design solutions and (3) the evaluation of the use of VR as a method for evacuation research of facilities that are not built yet, based on the realism of the scenarios perceived by the participants during the experiments.

As the FCC represents a unique facility which is currently under study, Virtual Reality (VR) experiments—a novel methodological approach in evacuation research [24, 25]—have been used to investigate different way-finding installations and the evacuation design concept of the FCC. Virtual Reality evacuation scenarios allow participants to experience a simulated emergency scenarios so that their behaviour can be observed.

Its use is proposed here as it presents several advantages for the evaluation of the effectiveness of different way-finding aid installations. In particular, VR allows people feeling present in a virtual environment [26], thus this experimental methodology is extremely suitable for unique facilities that are not built yet, as it would not be possible to investigate the behaviour of people in a simulated emergency scenarios in the actual facility. In addition, VR allows for high experimental control [27], thus giving the possibility to easily manipulate the environment and the evacuation installations present in the tunnel where the emergency scenario takes place.

Different VR technologies are available today that have been used in the context of tunnel evacuation research, including Cave Automatic Virtual Environments [16, 28], Head Mounted Displays (HMD) [9], mobile-phone powered head mounted displays [29], etc. The experiments presented here have been conducted with an Head Mounted Display technology (HTC Vive™, dual AMOLED 3.6″ diagonal screen, 1080 × 1200 pixels per eye, 90 Hz refresh rate and 110 degrees of field of view, and 6 degrees of freedom of movement) as it gave the possibility to conduct experiments directly on the sites where existing accelerators are located. This facilitated the recruitment of a population relevant to the study and permitted to perform experiments at different locations (as Head Mounted Displays are easily transportable).

Prior to starting the recruitment and conducting the experiments, ethical and legal clearance to conduct the experiments were granted by CERN and ESS. Once participants volunteered to take part in the experiments, background information about the possible risks associated with the experiment (e.g. possible nausea or dizziness during the navigation in the virtual environment) were provided. It should be noted that the research team at Lund University had also obtained (before the experiments were conducted) a decision from the regional Swedish ethical board that evacuation experiments performed in Virtual Reality do not present significant risks to health and safety, thus they do not need to go through national ethical review before being conducted. Nevertheless, an internal ethical evaluation was performed prior to conducting experiments to assess possible risks and those were communicated to the participants prior conducting the experiments. This evaluation also excluded from the experiments people who had epilepsy (this was included in the recruitment information). Participants were taking part to the experiments as part of their work, thus no financial reimbursement was provided to them. Personal data were stored according to data protection routines at the Department of Fire Safety Engineering at Lund University. Data access and the virtual environment can be requested contacting the corresponding author of the manuscript.

The VR environment consisted of a portion of a particle accelerator tunnel based on one of the preliminary designs of the FCC. It was originally drawn using a 3D modelling software (SketchUp™ version 2017) and then imported into a game engine (Unity3D™, version 5.6.3p2). The equipment represented in the virtual tunnel was based on those present in existing tunnel particle accelerators (e.g. the Large Hadron Collider at CERN, see Fig. 1 for a comparison of an actual tunnel accelerator and the FCC virtual environment).

Questionnaire responses were collected in order to have participants evaluating the VR experience and the realism of the virtual environment. The main behaviour observed in the VR environment related to the percentage of people who were compliant to the instructions provided by the way-finding systems in relation to the scenarios they were experiencing. This allowed a comparison between different evacuation designs as the scenarios included different way-finding installations. Participants were also given the opportunity to provide qualitative open comments on the evacuation scenarios and the virtual environment.

The VR experiments presented in this paper have given the possibility to compare and evaluate a set of way-finding systems for the FCC evacuation design. The designs provided a compliance to the instructions given ranging from 62.9% to 92.6%. The solution tested in scenario 3 (the combination of flashing lights and signage on the door plus the improved Train Inspection Monorail robot and the active signage) provided a compliance level which is significantly greater than the baseline design (i.e. flashing lights without the robot). Results suggest that the design including a combination of multiple evacuation installations and including active signage can significantly improve way-finding.

The use of Virtual Reality as a research method allowed the obtainment of a substantial amount of data since 102 individual way-finding behaviour were collected and 1224 responses (12 per participant) concerning the VR experience and perceived realism were obtained with a relatively good cost effectiveness. It should also be noted that since the FCC facility is a unique facility that has not been built yet, VR can be considered an ecologically valid methodology to collect data on human behaviour in evacuation emergencies [46]. While evacuation drills in actual tunnel accelerators would be valuable, such type of drills would not be possible as a configuration such as the one proposed for FCC today does not exist. In addition, it is very difficult to arrange drills in existing particle physics tunnels (e.g. the Large Hadron Collider at CERN) given their lack of accelerator down time.

Results should also be analysed in light of the fact that the Head Mounted Display adopted for the VR experiments has a field of view which is different than the one available to people in the real world. The natural field of view of a human is approximately 180 degrees, while the HTC Vive offers a 110 degree field of view. Thus the behaviour observed in such type of VR experiments which include the interaction with evacuation installations initially located outside the field of view (e.g. the Train Inspection Monorail robot) should be considered as a conservative approximation of the real world behaviour, i.e. people in real life might notice evacuation installations even more.

Results were collected recruiting participants at different tunnel accelerator facilities. It should be noted though that a portion of the participants taking part to the experiments at ESS were previously employed at CERN or had been working with accelerator tunnels (see section concerning participants), thus the two populations at CERN and ESS can be assumed comparable. For this reason, the assumption that the use of two locations for running the scenarios is not influencing the results has been made (this has also been tested statistically, see Sect. 3.2).

The ecological validity of virtual reality evacuation experiments can be linked to previous studies comparing human behaviour in VR and in reality [46, 47].. The results of these experiments are in line with previous experimental research conducted in the real world aiming at investigating some of the evacuation installations systems under consideration, e.g. active signage and flashing lights [14, 42]. In addition, as the evacuation installation systems mostly consisted in visual and acoustic systems, the VR environment represented a valid alternative to physical experiments (as results concerning physical interactions in VR would inevitably be less ecologically valid [24]). Given the great flexibility and repeatability of VR—i.e. allowing in a very simple manner to add evacuation installations in the virtual environment—such experimental methodology has been a valuable tool to address the research questions under consideration in this study.

The behaviour observed as well as the qualitative comments made by participants seem to suggest that the combination of multiple evacuation installations can increase instruction compliance, i.e. the likelihood that people would follow an instruction about their direction of movement tends to increase if such information is given by multiple systems. This finding is in line with existing human behaviour in emergency theories which state that people tend to take their decisions on the basis of multiple cues [48, 49]. In addition, the uncertainty associated with the identification of the meaning of the type of alarm should make safety designers reflect on the need to adopt a single evacuation alarm sound rather than multiple sounds associated with different threats (e.g. fire, radiological, etc.).

From a technological standpoint, the VR technology in use (an Head Mounted Display) has not given a high level of physical discomfort to participants and not a single participant quit the experiment because of it. Along with the fact that people are not exposed to a real emergency, this makes VR a valuable methodological tool for evacuation research from an ethical point of view. Future research may aim at improving the levels of insecurity, stress, fear and disorientation (and in general the level of perceived urgency) by adding additional stimuli to the scenario (such as olfactory or haptic feedback [50]) in order to further improve the validity of the results. Nevertheless, the trade-offs between ethical restrictions and realism of the experience should always be taken into consideration while conducting such type of evacuation emergency research studies [51]. It should also be noted that some participants who did not exhibit instruction compliance declared that were interested in testing the limits of VR, in particular considering the participants adopting a “gamer” approach during VR experiments. This limitation should be taken into consideration while attempting to use VR tools for training, e.g. serious games for evacuation training [52] and while analysing the results. Despite this issue, given the observed compliance to the way-finding instructions provided, results are deemed to be applicable for the FCC design.

Some considerations need to be made on the generalizability of results given the impact of the sample under consideration in the present evacuation experiments. Participants were recruited among people working in accelerator tunnel facilities (CERN, ESS and MaxIV) in an attempt to match the possible type of population present in such type of facilities. Given the scope of the study (the evaluation of the evacuation design for the FCC), such sample is deemed to be relevant and results applicable for the FCC. Nevertheless, care should be made in generalizing the results outside this population type as general public who is not familiar with particle physics facilities might have a different response to installations that are not familiar to them (e.g. the Train Inspection Monorail robot). A careful evaluation of the findings is therefore needed in order to generalize the results of this paper for other type of infrastructure facilities (e.g. road and rail tunnels) given possible differences in familiarity with the facility (as the population in road/rail is overall less familiar with the environment) as well as architectural features (e.g. differences in cross sections and typical use of the facility).

It is believed that future studies will investigate the links between the perceived realism and the behaviour in VR evacuation (this should be ideally performed investigating several VR experiments with different level of sophistications and resolution in the scenario representation). Future research should focus on investigating an increased number of evacuation scenarios and evacuation installations. For instance, this can include the study of different evacuation installations in isolation or the investigation of the impact of different combinations of installations using larger sample sizes. In fact, the current study includes an uneven number of participants for scenarios 1 and 2 as we had to discard four participants in one scenario because they did not interact with the way-finding systems at all, while the third scenario presented a lower number of participants due to recruitment issues (given the specific type of participants needed). In addition, VR experiments have been conducted with people navigating the virtual environment one at a time, while social influence can have a significant impact on evacuation performance, as demonstrated by previous VR experiments in tunnel evacuation scenarios [28]. Future studies should address how instruction compliance is affected by social influence, i.e. decision making in relation to the decisions of others [28, 44]. As the occupant load inside a tunnel accelerator is relatively low and the worst case scenario is actually the presence of a single individual in a tunnel accelerator (as previously investigated in [44]), the scenarios under consideration are still deemed to be relevant for the design of FCC. Future research should further investigate the interaction between evacuation installations and decision making in groups.

VR has been a powerful tool to compare evacuation installation effectiveness and investigate emergency scenarios in a unique facility that has not been built yet, the Future Circular Collider. The scenarios including different evacuation design concepts and way-finding systems were compared. Such scenarios represented the most suitable options for evacuation design in the FCC, thus having a direct applicability in the real world. Moreover, VR allowed testing different possible way-finding systems for this facility and indicated the most suitable design among the selected ones prior to implementation in the real world. As the results fall in line with previous real-world research on way-finding systems, the recommendations drawn from this study can be used for fire evacuation design. Results show that the combination of flashing lights, dynamic signage and a robot installed on a monorail provided a significantly better way-finding instruction compliance than a baseline scenario in which no dynamic signage and robot were installed.