This paper proposes a prescriptive model to formulate and evaluate a tsunami evacuation. The proposed method firstly establishes the evacuation scenario, which consists of defining the destinations of the evacuees, the starting time for evacuation and the evacuation mode. This scenario formulation is achieved by solving a linear programming problem. Subsequently, the scenario is evaluated by a time-dependent, multiclass assignment model. The proposed methodology was applied to the coastal area in Osaka city, Japan. Our main policy implications regard the permission of automobile usage for evacuation, a highly discussed issue in Japan. The results illustrate that some car usage can be allowed to facilitate fast evacuation but that excessive usage should be avoided under some conditions. We further suggest that it is not only the rate of car usage but also the timing of the usage of automobiles for evacuation that can be critical.