Queue Formation and Evacuation Modelling in Road Tunnels During Fires

This paper illustrates and describes the results of a modelling work on the effect of fire dynamics, queue vehicle formation, tunnel geometry on the evacuation modelling in road tunnels. The modelling approach is based on a CFD simulation of the fire development and interaction with tunnel geometry, the effect of vehicular blockage on smoke movement performed using the FDS code. Several simulations with the EVAC code (an agent-based egress model) are then performed to evaluate the evacuation strategies of the different tunnel users. The queue formation dynamics is evaluated using a specifically conceived model which is coupled with the FDS+EVAC codes to perform the modelling of users’ evacuation. Different key aspects have been analysed: 1) the influence of smoke on users’ movement speeds 2) the impact of modelling assumptions on the emergency exit choice 3) the effect of the queue formation model and distribution of the vehicles in the tunnel. The model also offers the opportunity to study the effect of emergency ventilation conditions and of the presence of different vehicles (cars, buses). This model approach is here compared and calibrated using the evacuation experiment that was performed in a road tunnel to investigate how occupants behave and respond when exposed to a fire emergency (Nilsson et al., 2009). The complete geometry of this emergency scenario was reproduced, including smoke generation, distribution of vehicles along the tunnel and location of the emergency exits. A satisfactory agreement was obtained, and a sensitivity analysis on model assumptions was performed to extract reference values for the application to new tunnels and different fire scenarios.