The incident chains in Table 2 can

The incident chains in Table 2 can to integrated into a network which can better capture the full complexity of multiple relationships among different sub-event and scenario. In this part, VOS Viewer software is used to assess the sub-event of SEIN. In order to map this network, the number of the sub-event in an escalator incident should not be less than 2. Finally, 472 records were excluded. The remain 327 records SEIN was analyzed. The labels and the map of part sub-events were shown in Fig. 3 for clearer observation, the whole map of 61 sub-events of SEIN was shown in Appendix A. The nodes are the sub-events identified in Table 1. The edges are the relationships between two sub-events. Edges means the relationship between two connected sub-events has direction because of the causal sequence between sub-events. An input direction means the sub-event is a result and an output direction means the sub-event is a cause.