In this paper is presented the prototype of a system designed to analyze roadaccidents. The analysis is carried out in order to recognize within accident reports generalmechanisms of road accidents which represent prototypes of road accidents. The adoptedproblem solving paradigm is the case based reasoning. Natural language documents andsemi-structured documents are used to create cases of our system. To cope with this difficultywe propose approaches integrating semantic resources. Hence, an ontology of accidentologyand a terminology of road accidents are used to build descriptions of cases. The alignmentof two resources supports the retrieval process. Based on models of accidentology, a dataprocessing model is proposed to represent cases of the system. This paper presents the architectureof ACCTOS (ACCident TO Scenarios), a case based reasoning system prototype. Themodel to represent cases of the system is introduced and the phases of cases based reasoningcycle are detailed.