## 6 Conclusions  
This paper uses the disturbance scenario of signaling system failure as the research background and analyzes the impact on the rail transit network after the disturbance. Firstly, the Space L method with the introduction of a virtual interchange edge is used to construct the urban rail transit network. Then, indices of two aspects, network topology and network operation performance, are selected, and the comprehensive evaluation method of the variation coefficient-VIKOR method is adopted to propose the evaluation method  
Figure 6: Distribution of critical stations. (**a**) Distribution of critical stations identified based on the original attack approach; (**b**) Distribution of critical stations identified based on the attack approach in this paper. of the importance of urban rail transit nodes in the signaling system failure scenario. The main conclusions from the case study are as follows. 1. This paper considered the structural characteristics and actual operation characteristics of urban rail transit, including the mutual independence of different line operations in the construction of rail transit networks and the failure mechanism of signaling system failure in the evaluation of node importance. This method can more comprehensively and objectively determine the value of the evaluation indices of each metro station and correct the impact of station failure on the network in technical disturbance scenarios. 2. The variation coefficient-VIKOR method is used to propose a comprehensive evaluation method of site importance, incorporating passenger flow as an important factor into the dynamic index of network operation performance and combining it with the dynamic index of network topology. This made the node importance evaluation results more objective and practical. 3. The method in this paper identified that 85% of the top 20 critical stations in terms of node importance are interlocking stations, and most of them are distributed in Nanjing Metro passenger flow backbone Lines 1, 2, and 3. Compared with the original attack method of identifying critical stations, the method in this paper can identify critical stations that are easily ignored by daily management, which are not necessarily the stations with the heaviest passenger flows or interchange stations in the metro network. The focused maintenance of these stations can minimize the loss of the network caused by the failure of the signaling system and guarantee the stable operation of the urban rail transit network. 4. On the basis of identifying critical stations using the method proposed in this paper, for the management and maintenance of the critical stations of urban rail transport, the management department should formulate a perfect emergency response plan to deal with emergencies occurring at the identified critical stations. For example, interlocking stations and ECC stations, such as Jiqingmen Street Station, Xinjiekou Station, Nanjing South Station, etc., should strengthen the emergency training of the staff and the management of the equipment to comprehensively improve the emergency response capability of the critical stations of the rail transport and even the rail transport network. Only in this way can the occurrence of disturbance events, such as signaling failures caused by various factors, be solved. In summary, it is recommended that the study on the evaluation of the importance of urban rail transit nodes be carried out in a specific disturbance event scenario. Considering the structural characteristics and operational characteristics of the rail transit itself, using the coefficient of variation-VIKOR method to evaluate the results is more objective and practical. The research in this paper can help the metro operation and management departments find the critical stations in a signaling system failure and protect them in advance, which can effectively reduce the frequency of failure and its negative impacts and further ensure the stable operation of the rail transit and the safe travel of passengers.