The Mass Evacuation (MASSVAC) model was originally developed for analysis and evaluation of evacuation plan in a specific area facing natural disasters. It was later applied to deal with the problems of evacuation around nuclear power stations (MASSVAC 3.0). The purpose of this model is to simulate the network clearance time and evacuation routes. In the process, it employs the Dial's or the all-or-nothing method to assign the traffic on to the network.

The major effort in this research is to include the user equilibrium assignment method to reduce the evacuation times and to improve highway network performance. Evacuation routes, number of links used, and evacuation times etc. are found to be influenced by the user equilibrium assignment method. Transportation System Management (TSM) strategies have also been incorporated in this enhanced model (MASSVAC 4.0) to improve the network performance during evacuation. The trip distribution process and the shortest path algorithm has been modified appropriately to suit the user equilibrium assignment.