# A Typology Model of Temporary Facility Constraints for Automated Construction Site Layout Planning
## 6 Discussion  
### Evaluation Percentages by Constraint and Temporary Facility Types  
Figure 9 is a stacked bar graph showing how CSLP planners consider the constraints identified in this study when performing CSLP by types of constraints and temporary facility. Figure 9: Evaluation percentages in overall (**a**), by constraint types (**b**), and by temporary facilities (**c**). First of all, 88% of all constraints were considered or worth considering in actual CSLP cases. However, note that 43% of these constraints were not considered in reality. This may have been because some constraints pose difficulties in detailed inspections without the help of computers due to the complex relationship between objects (e.g., DI3, RG9, IF11, and VI3). For example, in checking DI3, the minimum width of the access road should be determined taking into account various factors simultaneously, such as the curvature of the road, surrounding obstacles, and the vehicle size. Insufficient consideration of these factors often leads to either narrow access roads that generate traffic issues on-site or unnecessarily wide access roads that reduce free areas for other facilities and logistics. Another reason might be that some constraints have a large number of objects that need to be checked, causing repetitions in evaluation (e.g., IF7 and VI3). For example, IF7 requires a planner to check separation distances between all objects on-site, and such repetition is time-consuming and even error-prone. Therefore, to increase the actual consideration rate of the constraints, automated and computer-assisted construction checking needs to be realized to complement current repetitive manual checking practices for various constraints. As for constraint types, more than 90% of respondents said that the dimensional and regional-type constraints are to be considered, and more than half of them actually considered the constraints in their projects. It seems that the constraints have frequently been checked because these are closely related to civil complaints as well as smooth logistics and safety issues. Because the checking of these constraints still relies mostly on experience, intuition, and brainstorming of construction site layout planners, computer-based checking can help them review these constraints in an efficient and accurate way. Meanwhile, the percentage of actual consideration of inter-facility distance and visibility constraints was only 43% on average. This may be because they involve more than two objects in evaluation, which often requires complex or repetitive calculations. For example, the checking of VI3 can be quite complicated due to various factors such as the height and size of the objects. According to the interview, there were no cases in which a computer was used to examine the visibility. If the visibility checking and distance examination can be performed automatically using computer technologies, these types of constraints can actually be checked quickly, leading to quality improvement of construction site layout. As for temporary facility types, more than 93% of respondents said that the constraints related to gates and access roads are worth considering, which is considerably higher than the percentage of other temporary facilities. However, the actual consideration rate of the access roads constraints was only 60%. This may be because gates often have a priority in CSLP due to their impact on materials and equipment logistics, traffic outside the site, and civil complaints. On the other hand, constraints of access roads (e.g., VI1 and DI3) often require vehicle movement information, which is difficult to track without the help of a computer, such as vehicle turning radius, vehicle width, and vehicle safety buffer zone [46]. Compared to other facilities, laydown areas, storages, work areas, toilets, and parking lots also have constraints that are worth considering but not actually considered in practice.