Many nations are debating the implementation of vessel traffic services (VTS) and it is envisaged that some regulation of the movement of marine traffic may soon be imposed. It is highly desirable that prior to any change a rigorous appraisal of the existing traffic be carried out to establish the level of risk in the area; this level can then be used to evaluate any proposed change. The following note describes a research project concerned with establishing a general method of determining the base risk level, developed from earlier research by M. Degré and M. Lefèvre who used a computer simulation of marine traffic in the Dover Strait to assess the impact of various suggested traffic separation schemes. A cost-effective tool has been developed at Liverpool which will enable traffic patterns to be studied in areas remote from the land. This is a computer simulation model which is being used to establish dynamic areas of risk in the Irish Sea, which could easily be transposed to study traffic patterns in any other area.