At the last French/Spanish top meeting in Malaga after the Prestige accident (November 2002), these two countries have decided to exclude 'suspicious' vessels from their 200 miles Exclusive Economic Zone. 'Suspicion' about a vessel must not only be attached on the basis of static parameters such as her age, flag, class, number of crew, state of the hull, nature of cargo, etc., but also on time dependent elements like weather and traffic conditions which exist in the area of navigation of this ship. It is thought that such a dynamic ship's risk index may be built to assist in real time the VTM (Vessel Traffic Management) actors in the monitoring process of vessels sailing in their area of responsibility, using the concepts designed for Risk Assessment Models developed in the framework of FSA. This paper recalls first the objectives and the principles of such risk models. It will propose in a second part some developments made in the framework of the European project EMBARC about analytical formulation of a dynamic risk index to be attached to certain type of ships and the methods to define its value.