Method for determining a route minimizing the energy expenditure of a vehicle travelling within a road network, comprising the following steps: a) the current position and destination of said vehicle are identified; b) a dynamic model of said vehicle is constructed, which relates the energy consumed by said vehicle to the speed and to the acceleration of said vehicle; the method being characterized in that the following steps are carried out: c) a line graph of said road network is constructed between said identified position of said vehicle and said identified destination of said vehicle by implementing the following steps: i) a directed graph of said road network is constructed with nodes and arcs, said nodes of said directed graph corresponding to the intersections of said road network, and said arcs of said directed graph corresponding to the roads connecting said intersections; and ii) said line graph of said road network is constructed with nodes and arcs, said nodes of said line graph corresponding to the arcs of said directed graph and said arcs of said line graph corresponding to the adjacency of said arcs of said directed graph; d) the energy consumed by said vehicle is determined for each arc of said line graph by means of said dynamic model of the vehicle and an average speed of said vehicle on an arc of said directed graph associated with said arc in question and an acceleration of said vehicle to reach said average speed; e) said route between said identified position of said vehicle and said identified destination of said vehicle is determined by means of a shortest path algorithm which minimizes, on said line graph, said energy consumed, said shortest path algorithm being capable of taking into account, if applicable, a negative energy consumption on at least one arc of said line graph. a) the current position and destination of said vehicle are identified; b) a dynamic model of said vehicle is constructed, which relates the energy consumed by said vehicle to the speed and to the acceleration of said vehicle; c) a line graph of said road network is constructed between said identified position of said vehicle and said identified destination of said vehicle by implementing the following steps: i) a directed graph of said road network is constructed with nodes and arcs, said nodes of said directed graph corresponding to the intersections of said road network, and said arcs of said directed graph corresponding to the roads connecting said intersections; and ii) said line graph of said road network is constructed with nodes and arcs, said nodes of said line graph corresponding to the arcs of said directed graph and said arcs of said line graph corresponding to the adjacency of said arcs of said directed graph; i) a directed graph of said road network is constructed with nodes and arcs, said nodes of said directed graph corresponding to the intersections of said road network, and said arcs of said directed graph corresponding to the roads connecting said intersections; and ii) said line graph of said road network is constructed with nodes and arcs, said nodes of said line graph corresponding to the arcs of said directed graph and said arcs of said line graph corresponding to the adjacency of said arcs of said directed graph; d) the energy consumed by said vehicle is determined for each arc of said line graph by means of said dynamic model of the vehicle and an average speed of said vehicle on an arc of said directed graph associated with said arc in question and an acceleration of said vehicle to reach said average speed; e) said route between said identified position of said vehicle and said identified destination of said vehicle is determined by means of a shortest path algorithm which minimizes, on said line graph, said energy consumed, said shortest path algorithm being capable of taking into account, if applicable, a negative energy consumption on at least one arc of said line graph.