In any debate about the transport of dangerous goods where the effectiveness of existing legislative controls is challenged, it is very important that there is a full understanding of the magnitude of the risks involved and the causes and major contributors so that properly informed decisions can be made. This paper gives details of the methodology developed for the analysis of the risks arising from the carriage, in bulk, of toxic and flammable substances by road and rail as part of a major study into the risks faced by the British population from the transport of dangerous substances. This paper concentrates on the novel aspects of the study and in particular consequence and human impact modelling. Models are given for the interaction of passenger and dangerous goods trains taking into account the ability of signals and other systems to detect and stop approaching trains. In the case of road transport, the models allow for the characteristics of different road types and the behaviour of motorists to be simulated. The relative risks of transporting hazardous materials by road or rail are explored and it is shown that the inclusion of motorist and rail passenger populations significantly affects the calculated risk levels. It is concluded that the safe routing of materials with large hazard ranges may be more easily achieved by road. While, the natural separation afforded by the rail system may make this mode more suitable for lower hazard materials. However, it is concluded that in Britain, there appears to be no evidence to support, on safety grounds, a general transfer of hazardous goods from road to rail or the reverse.