In a disaster situation, functionality of a transportation network in populated areas is critical for effective emergency response. Unfortunately, disruptions affect these transportation networks’ components.  Critical network infrastructures, such as transportation networks on metropolitan areas, are vulnerable to intentional or unplanned disruptions, which may render some of their components (roads, highways, bridges, among other ground components) non-operational leading to deterioration of service due to path destruction and even disconnectedness (non-operational paths) between nodes that provide service and nodes that receive it. This research proposes to assess network functionality as the capability of the transportation network to provide a feasible path between emergency response providers and affected population.  The objective of this project is to understand and assess the effect of disruptions on network performance, considering disruption propagation among network components and uncertainty regarding which network components are in a failed state after disruption strikes. This research has the potential to enhance the ability of decision makers and practitioners to protect critical infrastructures of national interest, to better understand the effects of disruptions on network performance and to how different topologies tolerate them. Furthermore, the development of a probabilistic measurement applied to disruption propagation can be considered to future work.