## 3 Case Study: Structural Factor Analysis for Public Transportation Bus
### Discussion
#### 3.6.1 Summary of Analysis Findings
Factors with a low cause degree but a high centrality degree, i.e., engine speed sensor (CF8), diesel injector (CF9), engine cylinder (CF10), and electrical appliance central control system (CF29), while not primary drivers of failures are essential due to their crucial position within the system. In maintenance management decision-making, it is essential to prioritize these high-centrality, low-cause degree factors. Although the components involved do not often fail, their critical position within the system means that any failure can result in widespread disruptions. Therefore, it is essential to conduct regular and thorough inspections of these factors to ensure their proper functioning. Regular inspections can be conducted at a moderate frequency. Additionally, implementing preventive maintenance strategies can detect any early signs of potential failure and address issues before they cause widespread system disruptions. Regarding maintenance resource allocation, experienced technicians should be prioritized for the maintenance activities of components involved in these critical factors. An adequate inventory of spare parts is crucial to ensure swift replacements. Lastly, factors with both a low cause degree and a low centrality degree, i.e., brake system air hose (CF16), air brake dryer (CF18), balance lever (CF21), and shock absorber (CF22), have a minimal impact on the overall system. Such factors may not require as rigorous or frequent maintenance as those with higher cause or centrality degrees. However, such factors should not be entirely neglected as their failure can still lead to localized issues affecting specific functions of the bus. In maintenance management decision-making, basic-level maintenance activities can be implemented for such involved components to ensure their proper functioning. Regular inspections can be conducted at a lower frequency. Corrective maintenance in which repairs are performed after a failure occurs can be adopted. For resource allocation, fewer technicians can be assigned to perform inspections and maintenance. Additionally, an adequate but not excessive inventory of spare parts is sufficient to handle potential failures. For factors requiring attention within an effect group, their influence can be explained by their high effect degree, i.e., transmission computer (CF1), transmission (CF2), transmission speed sensor (CF4), water tank fan pump motor (CF5), and high-pressure fuel pump (CF12). While they may not be primary drivers of failures, their malfunction can lead to significant system-wide disruptions. In maintenance management decision-making, such factors should be closely monitored to detect early signs of issues. Rapid-response protocols should be established to swiftly address emerging problems, minimizing downtime and service interruptions. Conversely, factors within the effect group that do not generally require significant attention, i.e., ABS/ASR sensor circuit (CF13), air brake cylinder (CF17), handbrake/rear transmission safety cable (CF19), parking handbrake pump (CF20),suspension airbags (CF23), power steering fluid inlet hard hose (CF24), and power steering pump (CF25), have a lower impact on the overall system. The influence of these factors is limited to less critical areas. These factors can be handled with corrective maintenance and basic maintenance schedules. Resources do not need to be heavily allocated to these factors. By analyzing the importance and interrelationships of critical structural factors, practical maintenance management can achieve significant improvements in both the public transportation safety and maintenance efficiency. By prioritizing maintenance tasks about the factors with the higher impacts on vehicle failures, the escalation of minor issues into significant problems can be effectively mitigated, which can enhance overall public transportation safety and ensure citizens' well-being and travel experience.