Recent urban earthquakes, such as Loma Prieta and Northridge in the USA, and Hyogo-ken Nanbu in Japan, have demonstrated that damage to bridges causes serious functional loss of a transportation network system as well as life-safety risks and repair costs. This functional loss can result in critical impacts such as hindrance in the freight flow and passenger vehicle flow which will impact the regional and national economy as well as impact post-earthquake emergency operations. Moreover, the capacity to respond to concurrent threats would be severely eroded. This study presents a novel methodology for the assessment of network-wide impacts. Integration of state-of-the-art fragility curves and damagefunctionality relationships developed by Mid-America Earthquake (MAE) Center for bridges is undertaken to assess damage and capacity reduction in a stochastic framework. A Deterministic User Equilibrium (DUE) model is used to simulate traffic flow. Sampling techniques are proposed for evaluating the network impact. Illustrative examples are presented to demonstrate the procedure. The methodology presented in this paper, and the application cases, emphasize the importance of estimating the impact of earthquakes for direct mitigation planning by retrofit prioritization as well as for response in the event of an earthquake.