A method and apparatus for determining routes vehicles (4, 6), the method comprising: measuring positions of a first vehicle and a second vehicle (6); providing a specification of a region (12) having a fixed position in relation to the first vehicle (4); using the measurements and the region specification, determining a first route for the first vehicle (4) and a second route for the second vehicle (6). Determining the routes comprises: constructing a graph (34) within a joint state space (X) of the vehicles (4, 6); identifying, within the graph (34), a path from a first vertex to a second vertex, the first vertex corresponding to the measured positions of the vehicles (4, 6), and the second vertex corresponding to the second vehicle (6) being at least partially located within the region (12); and, using the identified path, determining the first and second routes.