## 4 Discussion
ECF142-UCA6 can be treated by \"a normalized operation procedure regarding the TIDS should be developed\". ECF143-UCA6 can be controlled by \"the driver should have the access to shut off the TIDS in some specific circumstances\". ECF138-UCA6 can be treated by \"the TIDS should provide enough reminder when it is not in the designed zone\". The control of ECF140-UCA6 can be \"signs should be placed alongside the track to remind the driver whether the section is suitable for the TIDS\". \"The driver should be trained to know how to distinguish the TIDS designed zone by all kinds of information\" can be taken for ECF141-UCA6. The ranking of the priority of these measures is the same as the importance ranking of the corresponding edges. * Figure 6 shows that CF75 (the TIDS does not recognize the localization sign) is a middle hazardous factor. This means resources should be allocated to both preventing it from happening and preventing it from causing others. Thus, both incoming and outgoing edges should be of concern. Table 3 shows that the ranking of incoming edges is ECF93-CF75, ECF95-CF75, ECF37-CF75, ECF61-CF75, ECF43-CF75, ECF48-CF75, ECF18-CF75, and ECF62-CF75. For ECF23-CF75, measures can be taken, for example, \"improve the image quality in different situations and make localization signs easy to be recognized from low-quality image\". ECF55-CF75 can be treated by \"the TIDS should reduce the recommended speed when the results from image recognition and LiDAR conflict\". Measures such as \"localization signs should be easy to be detected by the TIDS in different kinds of environment\" can be taken for ECF37-CF75. The control of ECF43-CF75 could be \"the computing performance of the TIDS should catch up with the operating speed of the train\". For ECF48-CF75, \"the appearance of localization signs should be designed to be easy for the algorithm to recognize\" could be taken. \"Localizationsigns should be placed in a way that suits the vision of the TIDS cameras\" can be taken for E\({}_{\text{CF18-CF75}}\). E\({}_{\text{CF61-CF75}}\) can be treated by \"the TIDS should provide proper recommended speed to ensure the localization signs are detected in a terrible environment\". For E\({}_{\text{CF62-CF75}}\), \"localization signs should be placed within proper distance to the train's route\" can be taken. More resources should be allocated to the measures that correspond to high-importance edges. Meanwhile, the ranking of outgoing edges of CF75 is E\({}_{\text{CF75-CF76}}\), E\({}_{\text{CF75-CF73}}\), and E\({}_{\text{CF75-CF77}}\). For E\({}_{\text{CF75-CF76}}\), measures such as \"the TIDS should reduce the speed limit and regain localization by detecting the next sign\" can be taken. \"The TIDS should evaluate the accuracy and correctness of its localization when a localization sign is not detected\" can be adopted for E\({}_{\text{CF75-CF73}}\). The control of E\({}_{\text{CF75-CF77}}\) can be \"additional localization signs should be placed in the areas with relatively high frequency where the TIDS misses localization signs\". Similarly, the measures for high-importance edges should receive more attention and resources. * As shown in Figure 6, CF142 (the improper operating procedure where the driver does not operate the on/off the TIDS when entering or leaving its designed area) is an initial hazardous factor. This means more resources should be allocated to the outgoing edges of this factor. As can be seen in Table 3, E\({}_{\text{CF142-UCA6}}\) is the more important one, followed by E\({}_{\text{CF142-CF145}}\). The control of E\({}_{\text{CF142-UCA6}}\) can be \"a normalized operation procedure regarding the TIDS should be developed\". ECF142-CF145 can be treated by \"proper procedure of the driver should be developed to monitor the working status of the TIDS\". Since E\({}_{\text{CF142-UCA6}}\) is the more important one of the two edges, more resources should be allocated to its corresponding measures. The discussion above demonstrates how to develop control strategies for high-betweenness hazardous factors.