Abstract As significant uncertainties are associated with the factors governing the operational characteristics of bridges following earthquakes, it is important to compute the reliability of transportation networks as a function of bridge fragility. A novel framework for the computation of transportation network fragilities following earthquakes is proposed herein, and the effectiveness of the proposed methodology is demonstrated using a hypothetical bridge network in California, USA. The proposed methodology affords the likelihood of functionality of bridge routes as a function of ground motion intensity. The network fragilities identified by this methodology can aid emergency responders and bridge owners in assessing the availability of possible routes after a seismic event based on the likelihoods of functionality of the routes.