The conception of “social force” was introduced to keep reasonable
distances among individuals in 1951. The social force model was proposed
by Helbing andMolnar [26] based on the fluid dynamics equation
in 1995,where the pedestrians were driven by three forces: namely the
desired force, the interaction force between pedestrians, and the interaction
force between a pedestrian and walls. The original social force
model of 1995 was improved by Johansson et al. [30] where an evolutionary
optimization algorithm was used to determine optimal parameter
specifications for the social force model based on suitable video
recordings of interactive pedestrianmotion and improved tracking software.
A simple social force model is shown in Fig. 1, where the corresponding
mathematical expression of each pedestrian i can be
represented by Eq. (1).