# Research on the Causes and Transmission Mechanisms of Railway Engineering Safety Risks
## 6 Risk Analysis of Railway Engineering Safety Based on Bayesian Network
### Occurrence Probability and Ranking of Risks' Key Causes  
Based on the Bayesian network structure for the key causes of railway engineering safety risks established in Section 6.1, the edge probabilities of 20 risk-critical factors were calculated. The edge probability calculation results were extracted and sorted from high to low according to the probability of occurrence of risk-critical factors, as shown in Table 4.  
### Occurrence Probability and Ranking of Risks' Key Causes  
Based on the Bayesian network structure for the key causes of railway engineering safety risks established in Section 6.1, the edge probabilities of 20 risk-critical factors were calculated. The edge probability calculation results were extracted and sorted from high to low according to the probability of occurrence of risk-critical factors, as shown in Table 4. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Serial** & **Key Risk Factors** & **Probability of Occurrence** \\ \hline
1 & Failure to perform supervision and management according to the standards for the safety supervision and management system (B\({}_{63}\)) & 0.278970 \\ \hline
2 & Internal railway personnel did not follow standard specifications for construction, loading and unloading, and maintenance (B\({}_{2}\)) & 0.253219 \\ \hline
3 & Internal railway personnel violated regulations during the construction, loading and unloading, and maintenance processes (B\({}_{1}\)) & 0.210300 \\ \hline
4 & Construction and other mechanical facilities and equipment encroach on limits, which affects the normal operation of trains (B\({}_{26}\)) & 0.147996 \\ \hline
5 & Inadequate supervision and management by responsible external personnel and supervisory units of the railway (B\({}_{9}\)) & 0.145923 \\ \hline
6 & The track rod breaks off or falls off, the number is insufficient, the geometric size exceeds the limit, the height and the curve positive vector exceed the standard, and the curve track is not smooth and round (B\({}_{13}\)) & 0.095410 \\ \hline
7 & The safety supervision and management system is not sound (B\({}_{62}\)) & 0.091093 \\ \hline
8 & The construction organization plan, construction effect, and actual demand do not match (B\({}_{61}\)) & 0.078435 \\ \hline
9 & Sleeper decay and failure, empty suspension with exposed head, loose upright bolts, and damaged shoulder (B\({}_{17}\)) & 0.046137 \\ \hline
10 & Failure to install the line safety protection facilities and measures according to the regulatory requirements (B\({}_{29}\)) & 0.040342 \\ \hline
11 & Security monitoring facilities and equipment are aging and in poor operational condition (B\({}_{33}\)) & 0.031529 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Statistical results for the probability of occurrence of risks’ key causes. Figure 3: Conditional probability diagram for the key causes of railway engineering safety risks. According to the sorted results, the probability of failure in supervising and managing the system in accordance with the defined standards for a safety supervision and management system (27.90%) was the highest among all the risk causes. Thus, the railway engineering department should enhance safety prevention awareness, improve safety supervision and management, increase the supervision and management level, and avoid safety accidents caused by non-standard management. In addition, it is necessary to pay additional attention to four aspects. First, internal railway personnel did not follow standard specifications for construction, loading and unloading, and maintenance (25.32%). Second, internal railway personnel violated the regulations during the construction, loading and unloading, and maintenance processes (21.03%). Third, the construction and other mechanical facilities and equipment encroached on limits, which affected the normal operation of trains (14.80%). Fourth, the supervision and management operations performed by the responsible external personnel and supervisory units of the railway were inadequate (14.59%).