This paper presents a framework to assess a performability measure in a urban transportation network given the possibility of an accident condition. This framework needs the evaluation of network performance during the accidental state. Such an evaluation is highly influenced by the duration of the accident and by information provided to the users during the accidental state. To model such conditions, we propose to solve a set of modified user-equilibrium problems. Results were obtained on a test network representing the links between downtown Montreal and the South-Shore suburbs. Accidents were studied on bridges linking the downtown area to the South-Shore.