Abstract:A computational model that simulates human behavior under fire and earthquake emergencies has been developed, using the object‐oriented language Smalltalk‐80. The present model consists of a space model, a scenario model and a human model. In the space model, the spaces in which people can move are represented by nodes connected by links. The nodes incorporate exit, guidelight and staircase facility data. Also, they feature environmental data including the darkness of the lighting system and the density of smoke. Seismic hazards such as a power failure and occurrence and expansion of fire and smoke are represented in the scenario model. This kind of information is then furnished from the scenario model to the space model as obstruction information. In the human model, a suitable knowledge‐based model has been constructed for representing evacuation behavior: people choose the evacuation path based on the production rules with certainty values, and move to the target exit along the evacuation links. The present simulation model is experimentally applied to examine the behavior which masses of people take in an underground structure under an emergency condition caused by an earthquake, and the results obtained confirm that the model is able to simulate correctly the principal human behavior enacted in an emergency evacu