The robustness of worldwide metro networks

The robustness of worldwide metro networks have been revealed by using random attack and target attack strategies. We find that the metro networks are more robust towards random attack. The robustness of those metro networks have also been compared with two model networks: random networks and scale-free networks. The metro networks are more robust than scale-free networks under target attack but more fragile under random attack. Comparing to random networks, the metro networks are vulnerable under both random and target attacks.