The NFPA-130 guidelines are very well established and widely applied. Its evacuation time calculations assume station occupant loadings, uniform conservative travel speeds and load balancing of exit routes. However, research shows that people's movement and behaviour is quite diverse and egress routes are partially chosen on familiarity.In order to investigate the sensitivity of evacuation times to these factors and enable designers to account for a number of human characteristics the computer model STEPS (Simulator of Transient Evacuation and Pedestrian movements) has been developed. It simulates and visualises the evacuation of people from building complexes such as underground and railway stations. The building's routes and populations can be defined with ease and flexibility.The paths through a building are managed using a hybrid network and grid configuration. Smaller confined routes such as staircases and passageways, assumed to be uni-directional paths during an evacuation, are treated as one-way arcs with lengths representative of the real situation. For larger areas a grid with suitable node width is overlaid and if necessary blocked-off regions positioned within it.The population is viewed as a collection of groups consisting of different genders and age ranges with appropriate values for patience and maximum travel speeds. Delay in initiating the evacuation and additional people arriving during the simulation from trains or cross-passages can be accounted for. Evacuees located on a grid, choose their exit routes based on four different criteria: (1) the shortest route, (2) familiarity with the exit, (3) crowding around the exit and their patience and (4) the routes' service rate.Toxicological effects on behaviour are, as yet, not accounted for, however studies into blocked routes due to smoke can be performed by adjusting travel speeds and the familiarity of exits.The validity of the model has been initially tested against the NFPA-130 calculations which show reasonable agreements in the evacuation times achieved. In addition, two further station scenarios are used to illustrate the capabilities of STEPS. Further investigations and model enhancements such as fully accounting for smoke hazards and incapacitation will be performed.
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