A robust potential-based route choice model for simulating pedestrian evacuation

In this paper, a cellular automata model for pedestrian evacuation is presented. Special attention is paid to a phenomenon wherein an artificial and allegedly unrealistic bias in route choice is introduced. This phenomenon is caused by the so-called gray areas that affect the calculation of the potential fields which dictate pedestrians' movements between lattice sites. In this paper, the concept of gray areas is formulated and the influence of the gray areas on the route choice is investigated for the first time. In brief, gray areas are those specific zones that should not influence the route choice behavior of pedestrians because they in fact cannot improve or deteriorate the evacuation safety, comfort and efficiency at all. To make the cellular automata model more robust to the gray areas, a new model is proposed based on a previous one, in which three factors including route distance, pedestrian congestion and route capacity are considered in the computation of the potential field. By changing the definition of route capacity from an exit dependent route capacity to be a path dependent one, the proposed model is not only comparable to the previous model in the sense of generating a wide range of route choice modes, but also more robust than the previous one when applied in the scenario containing gray areas. Such robustness is reflected in two aspects. First, the route choice patterns generated by the proposed algorithm are free from artificial and allegedly unrealistic bias in scenario with gray areas. Second, the route choice patterns generated by the proposed algorithm are less influenced by the extended gray areas and are closer to the optimal route choice. These two aspects are further confirmed by a comparison study with a finely validated perception-based model. Moreover, sensitivity analysis reveals that the proposed model is able to generate a wider range of route choice patterns. Finally, the results from the proposed model and empirical data are compared to show the effectiveness of the model in reproducing the route choice patterns observed in the reality.