This article provides a spatial and comparative approach to evaluate the territorial accessibility in the event of a volcanic crisis in the French West Indies. A spatial assessment of resources and populations exposed to volcanic hazards is performed, followed by an assessment of the risk of territorial isolation due to lahars. Modelling of the risk of terrestrial isolation builds upon graph-based computations and indices that take into account the specific vulnerability of river-crossing structures and the knowledge of historical lahars. Another application of the graphs concerns scenarios for the evacuation of population, the sole efficient response to an eruption. This results in an optimised division of areas to evacuate in order to assess the potential reduction of the load on the road network. These different results are integrated into a prototype for evacuation maps intended for local authorities. The situation of Guadeloupe is of greater concern than that in Martinique, given the level of exposure, the potential losses of accessibility in case of lahars, and the greater and ongoing volcanic unrest of La Soufrière volcano in Guadeloupe.