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Validation of a Legion simulation
Validation of a Legion simulation
Validation of a Legion simulation

Broadgate West

Multi-storey buildings, like London's Broadgate West, present planners, occupants and emergency services with the necessity for safe and timely evacuations. Different patterns of usage, layout and occupancy levels (by floor and also by day of the week) fuel debate about stairwell widths, the size of exits and evacuation strategies, among others. Could Legion simulations shed light on these issues? Are their outputs robust enough to be trusted? To answer these questions, the London Fire Brigade asked Legion, on two separate occasions, to film and model fire drills at Broadgate West: a nine-storey office block in the City of London. Phased (separate floors) and simultaneous (all floors) fire drills took place in May 2005 and July 2006, respectively. In each case the LFB tested six different scenarios and Legion filmed the entire experiment, using 25 cameras. The cameras had coverage of the stairwells and corridors, all the way to the outside congregation area. Legion was allowed to measure the individual speed of a small sample of evacuees but was then asked to simulate the drills without further information. Comparisons of video footage against Legion simulations revealed excellent agreement between reality and model: errors in the time taken to evacuate ranged between 3% and 13%, with an average of 6.8%. Viewing the video footage side-by-side with the simulations, the most impressive result was the similarity in the way space was used by real people and simulated pedestrians alike. For example, where two lanes of people merged into one in the footage, the same behaviour was seen to occur at the same point in the simulations. In light of these results, the London Fire Brigade "actively encourage using simulations for planning purposes" and they continue to provide regular input into Legion's product development cycle.