## 1 Introduction
### Literature Review
#### 1.2.1 Exit Width, Exit Location, and Bottleneck  
Discussions on exit width and exit location regularly appear in the form of its influence on evacuation time in emergency evacuation issues. The authors of [5] emphasized that four influencing factors, that is, total evacuation distance, evacuation speed, width of exits, and personnel density, could heavily impact the total spending time. The authors of [6] considered factors including the spatial distance, occupant density, and exit width to solve the problem of multiple exit choices for pedestrians. Some scholars have provided a similar conclusion in that modifying individual speeds and the average minimum width of the stairs could potentially reduce the overall evacuation time by 50% [7].  
Furthermore, some works have investigated how to obtain the optimal exit width under a given constraint of evacuation time. The authors of [8] presented a method of computing the optimal width of exits to improve the safety of pedestrian evacuation and the utilization efficiency of emergency exits in pedestrian walking facilities. The authors of [9] paid attention to the phenomenon called the faster-is-slower (FIS) effect though implementing experiments. They found that the FIS effect could be effectively prevented when the width of an exit is twice the size of the particles. The authors of [10] proposed a two-dimensional Cellular Automata (CA) model to simulate the exit evacuation dynamics and state that the total flux of an exit is an increasing nonlinear function of exit width, which can be used to calculate the optimal exit width. The authors of [11] considered the issue of exit width in scenarios with obstacles. The sensitivity analysis of various variables indicates that the distance between the obstacle and the exit, the obstacle size, and the exit width are three key factors. The evacuation effect is optimal when they equal to 1.25:1:1 under the 30-degree corner exit. The authors of [12] discussed different exit widths and found that the evacuation time decreases with an increase in exit width, and it tends to be stable when all exits have a width of 2.5 m. The authors of [13] analyzed four size-related parameters of convex exit, namely, the width of the bottleneck at passage, the passage size, the passage length, and the exit width, to determine the optimum design of the convex exit.  
Additionally, the exit location can also affect the total evacuation (travel) time. The authors of [14] aimed to present new software that provides all possible combinations of optimization for the exit door location. The authors of [15] believed that the number of evacuees differs for different functional spaces, resulting in uneven distributions of evacuees in the building plan. Thus, they proposed a design optimization method for exit locations based on BIM and ontology to provide exit location redesign plans to make the evacuation time shorter. The authors of [16] established an Artificial Bee Colony (ABC) optimization algorithm based on the stochastic method to find the optimal locations of the exit doors. This method overcomes the main limitation of the tedious process of handling multi-room problems and more complex room arrangements. The authors of [17] emphasized the relationship between the optimal value of f and building size to improve the performance-based design of building exits.  
The area near the exit often becomes a bottleneck that is crucial for emergency evacuation. Moreover, the design of the exit will directly affect the bottleneck size [18]. The authors of [19] carried out experimental research to analyze the influence of emergency signage and crowded bottleneck areas. The authors of [20] introduced an emergency evacuation model for limited spaces to examine the evacuation efficiency, density of the bottleneck area, escape route, and other important factors based on different exit widths.