Case I: different evacuation processes of one trial with different friend-group densities: (a1)–(a4) low friend-group density where the proportion of pedestrians in groups to total pedestrians is only 20% and (b1)–(b4) high friend-group density where the proportion of that is as high as 80% at different time steps: (a1) and (b1) step = 0, (a2) and (b2) step = 200, (a3) and (b3) step = 400, and (a4) and (b4) step = 600. The initial number of pedestrians in the waiting hall is 600 in each situation. Here, P_in donates the number of pedestrians left in the waiting hall and P_out donates the number of pedestrians escaped from the waiting hall at the specific time step.