The representation of evacuation movement in smoke-filled underground transportation systems

Limited guidance is available to engineers on how people's walking speed in smoke can and should be represented in the fire safety design process of underground transportation systems, such as road and rail tunnels. To address this issue, the behaviour and movement of people in case of evacuation due to a fire in underground transportation systems has been investigated. In this paper, the relationship between walking speed and visibility conditions has been analysed by performing a systematic review of current experimental research conducted in the field. This includes data-sets collected in Sweden, Japan, UK, Norway, Finland, Canada, and The Netherlands. A design recommendation on how to represent walking speed in both smoke-free and smoke-filled environments is presented. Uncertainty in data is thoroughly discussed and addressed in the recommendation. Three different methods to represent walking speed during the design of an underground transportation system are suggested. The selection of the method depends on the required treatment of uncertainty in the design. The developed representation substantially differs from existing methods used in fire engineering design to represent walking speed in smoke since it describes walking speed as a function of visibility, rather than the extinction coefficient. This permits comparison of data-sets collected in relationship to the presence of reflecting or emitting lights. Finally, suggestions on future research to be conducted in order to reduce the current uncertainties are provided.