The results of the online survey indicate that the sample, made of 234 respondents from 41 countries, is aware of a total of 72 computer pedestrian evacuation models. However, only 15 of these models are known by at least 10% of the sample: Pathfinder [17], FDS+Evac [18], STEPS [19], Exodus [20], Simulex [21], MassMotion [22], Legion [23], VISSIM/Viswalk [24], EVACNET [25], EGRESS [26], Pedestrian Dynamics [27], SimWalk [28], FPETool [29], Evacuationz [30], EVACSIM [31] (Fig. 2). This highlights most people are not aware of all the available pedestrian evacuation models. From a model selection viewpoint, the results suggest that the 12 most commonly used pedestrian evacuation models are: Pathfinder [17], STEPS [19], MassMotion [22], VISSIM/Viswalk [24], Pedestrian Dynamics [27], Legion [23], FDS + Evac [18], crowd:it [32], Simulex [21], Exodus [20], EGRESS [26] and EvacuatioNZ [30] (Fig. 3). Furthermore, the data indicates that a significantly higher number of respondents use Pathfinder (35%) compared to any other pedestrian evacuation model. The data also suggests that despite the large number of models available (over 60 models), a limited number of models seem to be the most used.
Several potential factors may contribute to the increased awareness and usage of given pedestrian evacuation models. First, the age of the pedestrian evacuation models can affect the results as some are much older than others which could mean they have had longer to build a user base. The second factor is the regional use of models in relation to the sample of respondents and type of sample respondents (mostly in the fire safety engineering industry). Third, regional marketing/sales can impact pedestrian evacuation model awareness as generally the most used models have agreements with resellers which can have varying scales of operation and impact in different regions. Fourth, the level of sophistication and continual development of the models can have an impact as the most used models may offer more features and may be more continuously updated compared to others. In addition, some of the models were developed for academic/research purposes and have limited marketing for wide spread adoption within the fire engineering industry. Another influencing factor relates to the free general academic/research use and subsequent wide spread tuition/adoption in fire engineering courses at universities which has grown significantly in recent times since the previous survey. Conversely some of the models are not freely available for general academic use or taught at universities which may influence awareness and usage. Pedestrian evacuation model developers whose models ranked low in the results may look to increase awareness/usage of their models through adopting/improving some of the items listed above.
General and practical factors affecting the selection of pedestrian evacuation models were investigated (see Figs. 4 and 5). Identical to the results of the 2011 survey, the data indicates that the most important general factor affecting the selection of a pedestrian evacuation model is the verification and validation: the level of reliability a model has to accurately represent reality is of key importance to users. It is evident a number of pedestrian evacuation model developers also agree with many of them producing dedicated validation and verification documentation or publishing papers presenting results of validation case studies, see for instance [35,36,37,38,39]. Furthermore, the development of international efforts to provide standard methods for conducting validation/verification of evacuations models [40,41,42,43,44] (including an ongoing effort performed within the Technical Committee 92 on Fire Safety of the International Standards Organization, ISO), will facilitate users being able to asses and compare more easily pedestrian evacuation models. The data indicates that users ranked the second most important factors when selecting a pedestrian evacuation model were jointly Data Output, Documentation, and Continual Development of the model. This would appear to be closely aligned with validation/verification which requires data output, documentation, and continual development. In contrast, respondents stated the most popular practical factor when selecting a model is trust in the research done to develop the pedestrian evacuation model. This is closely connected with main factor for selecting a model being verification and validation. Indeed, the basis for verification and validation is research which provides data that models can be developed and compared with. This suggests it would be advantageous for pedestrian evacuation model developers to invest more resources in research and data collection which can be used for validation and continual model development in order to provide users with increased confidence for using their models. Finally, it should be noted that part of the sample might not have known the difference between “CAD files importing” and “Integration with Building Information Modelling (BIM)” considering that 12% of respondents said they did not know what BIM is.
Regarding the types of usage pedestrian evacuation models are used for, results indicate that more than 60% of the sample use pedestrian evacuation models to assess whether buildings are compliant with codes/standards and to aid in the design of new structures. Commonly pedestrian evacuation models are used where a building design cannot meet prescriptive fire requirements and so performance-based design is adopted in order to demonstrate people can evacuate before untenable conditions occur. Alternatively, pedestrian evacuation models may be used to compare evacuation results of a building design which is complaint with prescriptive fire requirements with the actual building design (which is not compliant with prescriptive fire requirements) to assess if there is any significant difference in the results. Considering building design teams are developing ever more novel structures and pushing the technological boundaries of building design which may mean compliance with prescriptive fire requirements is challenging, it is unsurprising that the majority of pedestrian evacuation models are used for new buildings. What is perhaps surprising is that almost half of responses stated that pedestrian evacuation models were used for assessment of existing buildings. This may include where upgrade works or renovations/re-designs cause a non-compliance with prescriptive fire requirements. In both cases pedestrian evacuation models may initially be run and required to be re-run multiple times as the design changes. As such, the ease with which the pedestrian evacuation model allows users to make updates to a model is important to users which is supported by the data as the third most important factor when selecting to use a pedestrian evacuation model. This suggests pedestrian evacuation model developers should consider improving clarity with user interfaces and clear/simple work flows of how to change models (e.g. ideally with fewer clicks) in order to improve usability of the software.
The most common building types pedestrian evacuation models were adopted/used were train/metro stations, shopping malls, and arenas/stadia. This is unsurprising considering train/metro stations may be located deep underground and present a significant challenge for egress with large numbers of people being required to evacuate upwards (unlike most other types of buildings which downward evacuation is more common) [45]. Upgrade works to existing/older train/metro stations which potentially may not fully comply with the latest prescriptive fire requirements is also common, as such performance-based design may be adopted. Similarly, shopping malls and arenas/stadia typically contain large indoor enclosures where the potential for smoke spread during a fire is increased. Such spaces commonly exceed maximum fire compartment sizes within prescriptive fire requirements, so performance-based design is also commonly adopted. Considering these results, it may be advantageous for pedestrian evacuation model developers to review the workflows of users developing models of such types of structures. This may facilitate identification of potential areas where new features could be developed, or workflows optimised to support model applications for these building types.
In terms of how often respondents use pedestrian evacuation models, there is a wide range of frequency with which different people use pedestrian evacuation models. Just over a third of respondents (37%) use models at least once a week which potentially reflects users’ jobs as heavily focused on using pedestrian evacuation models. Finally, it was observed that more than 40% of the respondents had the need to use more than one pedestrian evacuation models as there are different needs for different projects and users select the model which is more suitable for the project goals (Fig. 8). This suggests it may be advantageous for pedestrian evacuation model developers to consider such users (who may not always need access to a given model) by offering temporary licensing options or ‘pay per use’ options for model usage in order to provide financial flexibility in their use. This could also increase breadth of adoption for such pedestrian evacuation models with it being more financially viable to use multiple models for a company (rather than being financially obligated/biased to use the model which a company currently pays a license for).
A novelty of this study is the investigation on how users got were trained in how to use models, the reason why they might stop using a model, and the use of BIM tools. The results indicate that the large majority of the sample were self-taught how to use pedestrian evacuation models using tutorials and documentation while only 20% and 16% of the sample stated that they attended short or long courses on this topic (Fig. 9). The data also highlights that costs, lack of upgrades, likelihood to get a project approval, and usability represents the most common reasons motivating the change of pedestrian evacuation models (Fig. 10). Finally, the respondents indicate that they would like to have BIM tools to facilitate their analysis and save time (Fig. 11). As such, the expansion of the original survey provided new insights on the user needs. However, future versions of this survey need to investigate other questions concerning other features of pedestrian evacuation models, such as the interactions with fire models and transport models. In addition, future surveys may look to sample of other decision makers (i.e. senior company managers) rather than modellers as target groups in order to investigate their perspectives on modelling in light of their experience in the industry.
A comparison of the survey results was conducted with the previous survey results published in 2011 by Ronchi and Kinsey [8]. It is worth highlighting that the top three known pedestrian evacuation models in the current survey are among the most well-known models in 2011 [8]. Figure 12 illustrates how the percentage of users for STEPS and FDS + Evac are consistent while the awareness and usage of Pathfinder has significantly increased since the 2011 survey. The comparison regarding the general factors affecting model selection shows that the first eight factors have an identical order in both surveys. It is worth highlighting that the sample in 2018 is slightly different from the sample in 2011. The 2011 survey included slightly less respondence (198 compared to 234) coming from a slightly narrower range of countries (36 countries compared to 41). Furthermore, the current survey was only provided in English given the limited number of responses obtained in languages other than English in the 2011 survey. The results from the current study are largely consistent with the 2011 study which suggests the impact of any difference in survey dissemination/sampling between the surveys is of negligible impact. It should be highlighted that the authors’ affiliation being focused in the fire engineering field may have skewed the sampling to respondence from a fire engineering background. Indeed, the primary target respondents of the survey are those from a fire engineering background. However, it should be noted that respondents originated from a wide variety of countries (41 countries) and only a 62% of survey respondents stated they worked in the fire engineering domain, thus findings should not be considered only being applicable to the fire engineering community. Further investigation is required to determine if and to what extent how a greater representation of non-fire engineer respondence would impact the results. Indeed whilst many of the pedestrian evacuation models listed in the survey are also used primarily for general pedestrian modelling, it is uncertain if the results from the survey are applicable to general pedestrian modelling outside of the fire engineering field (e.g., urban planning, comfort analyses and pedestrian flow optimizations in normal conditions). This is considered beyond the scope of the current study.