Recent years show an increasing number of people who use regional public transport, resulting in higher pressure on the operators. This increased pressure results in more disruption for passengers. This paper aims to develop a methodology for estimating the criticality of assets in a regional public transport network, taking the Rotterdam tram system as an example. The consequences of disruptions of each asset in the network are analysed by calculating the effect the disruption has on the average path length for all passengers. Each asset in the network is disconnected one by one to simulate this breakdown. The lines used in Rotterdam are analysed using real passenger data. Results show that 'Erasmus brug' is the most critical asset in the network, as expected by experts from RET. Aside from this, the model presents that the assets around 'Rotterdam Centraal' are less critical than expected because of the alternative routing options for the trams and passengers. This highlights that using this model can give new insights into critical assets in networks.