# Automated Generation of Daily Evacuation Paths in 4D BIM
## 4 Framework and Algorithms for Automated Generation of Evacuation Paths in 4D BIM
### Proposed Framework  
Figure 1 illustrates the proposed framework comprising five steps that are \"updating 4D BIM\", \"preparing user input\", \"generating evacuation paths\", \"reviewing and selecting paths\", and \"distributing the information in selected paths to related crews\". **Step 1: Update 4D BIM:** An updated 4D BIM is an essential system input that presents current progresses and configuration of the construction site. There have been research studies ([PERSON] et al. 2009) to track construction progresses automatically and reflect the results in 4D BIM. However, automated progress tracking is out of the scope of this research. This research assumes that the input 4D BIM properly reflects construction progresses, configuration, and shape of a current construction site. Therefore, users of this system should manually track current construction progresses and reflect them in 4D BIM. **Step 2: Prepare user input:** Using the case study of a real construction project, the authors identified key parameters that can impact the calculation of possible pathways within the interactive BIM-based path planning system. The parameters are used to develop rule-checking features for finding out the shortest path and a shelter within a building or a construction site. Even though the listed variables are not the formalized criteria or standardized requirements for calculating evacuation paths, the variables identified from a real construction project are essential for implementing the proposed 4D BIM-based evacuation planning. The list of parameters will be a great initiator that can establish a generalized list of variables in future research that must be considered to assess evacuation paths using 4D BIM. However, because of varied processes and requirements of construction projects, the formalization of such variables and key factors impacting pathfinding were not conducted in this research. The considerable parameters of evacuation planning that the authors identified from the case study involve the following factors:  
* Exits that allow work crews to escape from a construction structure and a jobsite
* Secured spaces that can prevent structure collapse, fire, or flammable gas
* Conditions of paths such as accessible or movable paths (e.g., A rebar work location is not an ideal pathway)
* Workspaces of onsite work crews that can impact site congestion and the flows
* Existing structures and objects that can block the pathway of workers
* Interference of workspaces that are crosslinking planned
* Stacked materials that are supposed to be instantly used for construction works
* Various types of equipment being used near construction tasks
* Temporary structures such as scaffolding  
The information about construction activities, equipment, materials, and site conditions are generally documented by a field manager or a superintendent on a daily basis to monitor work progresses. This research was conducted with the assumption that such information can be added as user-defined parameters on 4D BIM models to represent the most recent construction site conditions. **Step 3: Generate all available evacuation paths:** Based on the two system inputs prepared in step 1 and step 2, the BIM-based path planning system automatically identifies and quantitatively evaluates all available evacuation paths between work locations and exists. In this research, to identify the shortest evacuation path, a distance was considered as a primary criterion. **Step 4: Review and select evacuation paths:** In this step, superintendents and crews' qualitative reviews automatically generated evacuation paths and selected the paths to be used during construction. Both the path visualization in 4D BIM and the quantitative evaluation of all available evacuation paths assist in the decision making process for the most accessible and secure path.