The Effect of Person Order on Egress Time: A Simulation Model of Evacuation From a Neolithic Visitor Attraction

Objective: The aim of this study was to model the egress of visitors from a Neolithic visitor attraction. Background: Tourism attracts increasing numbers of elderly and mobility-impaired visitors to our built-environment heritage sites. Some such sites have very limited and awkward access, were not designed for mass visitation, and may not be modifiable to facilitate disabled access. As a result, emergency evacuation planning must take cognizance of robust information, and in this study we aimed to establish the effect of visitor position on egress. Method: Direct observation of three tours at Maeshowe, Orkney, informed typical time of able-bodied individuals and a mobility-impaired person through the 10-m access tunnel. This observation informed the design of egress and evacuation models running on the Unity gaming platform. Results: A slow-moving person at the observed speed typically increased time to safety of 20 people by 170% and reduced the advantage offered by closer tunnel separation by 26%. Using speeds for size-specific characters of 50th, 95th, and 99th percentiles increased time to safety in emergency evacuation by 51% compared with able-bodied individuals. Conclusion: Larger individuals may slow egress times of a group; however, a single slow-moving mobility-impaired person exerts a greater influence on group egress, profoundly influencing those behind. Application: Unidirectional routes in historic buildings and other visitor attractions are vulnerable to slow-moving visitors during egress. The model presented in this study is scalable, is applicable to other buildings, and can be used as part of a risk assessment and emergency evacuation plan in future work.