# An Agent-Based Simulation to Minimize Losses during a Terrorist Attack
## 4 Model
### Design Concepts  
The model simulates a real metro station in Tokyo (Kodemmacho). The station is modeled on real scale based on data provided by the metro dispatchers themselves via email communication. The trains run on a real-time schedule, with the model starting at 8:00 A.M. when the attack was committed. The duration is set at 35 min, after which time the entire Hibiyo line was closed and people evacuated.  
The first train arriving at the station will cause the source of the sarin to be kicked off the platform and the start of gas to air. The spread of sarin occurs in a discrete environment. One cell is a source of infection, and the gas continues to spread to cells in its eight connected neighborhoods. It is modeled using a state diagram where each cell can acquire an infected/uninfected state. If a cell gets infected by a received message from another cell, internal transit in that state causes it to spread to other cells by sending messages to its neighbors. In the infected cell, the density of the sarin is continuously added based on its distance from the source until the density value is equal to the maximum concentration calculated by function.  
People appear to be classic passengers who either arrive at the metro station and wait for the train, or arrive at the station by train and leave the station by the nearest exit. Their behavior is mainly based on empirical data. The entrance to the metro is subject to the passage of the turnstile. At the same time, part of the population will be delayed by scanning the ticket (max. 3 s) and some passing immediately (assuming a prepaid card). The number of people at the station is influenced by the fact that the attack occurred in the morning rush hour and calculated from real values according to the average increase in the morning rush hour [24]. The station is set to the default number of people, as the model starts under regular metro operation. Since only the infection of individual people is monitored, people do not communicate with each other in any way.  
One hundred times per second, the position of each person is checked, and the degree of infection is added based on the density of the sarin in the area where it is. The calculation formula is determined from the known lethal dose of sarin, which is 100 mg-min/m\({}^{3}\). Thus, if there is a 100 mg/m\({}^{3}\) density in the box where a person is present, the person will reach the lethal value in one minute. If the value is smaller, the amount is recalculated. The time step is designed so that the model is as accurate as possible, but at the same time, it takes into account computational demands.  
People are then divided into three groups based on the degree of exposure.  
* Light exposure--miosis, mucus in the nasal cavity, bronchoconstriction, choking. Marked in white in the model.
* Severe exposure--miosis, mucus in the nasal cavity, bronchoconstriction, heavy choking, loss of consciousness, convulsions, seizures, spontaneous muscle twitching, weakness etc. Marked in yellow by model.
* Lethal exposure--with a so-called lethal dose of sarin, 50% of the population exposed to this dose will die. In experimentation, the total value of the infected is divided by two. Marked in red in the model.  
Given the purpose of the model, only the inhalation is taken into account. Absorbed through the skin, the risk is many times smaller and the infection would last considerably longer than the duration of the model, so it is not included in the model.