Novel two-layer cascading failure model for the vulnerability assessment of an interdependent traffic-power system

Urban Critical Infrastructures (UCIs) are exposed to cascading failures due to their internal connectivity and the complex interactions across physical, logical, geographic and cybers. Assessing the vulnerability of UCIs is essential for ensuring the reliable and safe operation of cities. Considering the specific UCI model of the interdependent traffic and power systems, this paper proposes a two-layer cascading failure model for assessing the vulnerability of the Interdependent Traffic-Power System (ITPS), consisting of a Traffic Layer (TL) and a Power Layer (PL). A user equilibrium model is used to simulate traffic flow in the TL, while the PL applies Kirchhoff’s laws for power distribution. To enhance the realism of interdependence modeling between the two layers, a Local Flow Entropy (LFE) interdependence method is introduced, integrating the flow states of neighboring components within the infrastructures. A case study on the IEEE118 system and Watts–Strogatz (WS) network demonstrates that the degree of ITPSs vulnerability is higher than under traditional Node Degree (ND) method in initial intentional attacks. The results show a nonlinear relationship between infrastructure capacity and vulnerability, highlighting the need for risk management strategies to balance cost and system stability.