This article was written in collaboration with WSP Principal Consultant Katja Berdica and WSP Senior Consultant Christian Nilsson. It was first presented as a part of the 8th edition of the International Symposium on Tunnel Safety and Security (ISTSS) in Borås, Sweden.
When designing exits from underground rail stations and evacuation routes from tunnels, the evacuation capacity is often the main dimensioning factor. In today’s practice (in Sweden), the typical criteria is that two crowded trains can be evacuated well before critical conditions arise. This can in turn result in unnecessarily high building costs or great uncertainties in projects. The purpose of the feasibility study is to explore the possibilities of finding an alternative approach to establishing the dimensioning passenger load, using guidelines based on traffic forecasts. An alternative approach is presented as a calculation example for a future commuter train station outside Stockholm, using forecast data in combination with existing statistical data for a similar station in operation today. In short, forecast models give the number of passengers that are expected to use a station on an average day. Statistics can be used to calculate how the maximum number of passengers relates to the average number. Hence, by combining forecast data with statistical data the expected maximum (dimensioning) passenger load can be established. The alternative approach is found to be more nuanced compared to the ”traditional” method for establishing dimensioning passenger load currently used, and seems to be a plausible way forward.
Finally, risk perspectives, uncertainties in forecasts and statistics connected to the alternative approach are discussed, followed by some suggestions for continued work in order to develop the line of thought further and formulate a working methodology.