Exploring the robustness of urban bus network: A case from Southern China

•Changsha urban bus network (UBN) has scale-free network topological properties.•Integrating attack- and node-based methods, the robustness of UBN are studied.•Intentional attacks are more destructive than a random failure.•Cascading attacks are more disruptive than normal attacks in the UBN.•Key nodes identification methods play a critical role in the robustness of UBN.