A vehicle navigation system computes an optimal route for a journey. When the system detects that a vehicle has deviated from the optimal route, information that tells the driver of the deviation of the vehicle is displayed. When the driver turns on a recomputation command switch after reading the information, a new optimal route is computed, with the vehicle's present location as the new starting point. If the vehicle deviates again after computation of the new optimal route, another new optimal route is automatically recomputed, again with the vehicle's present location as the new starting point. The driver is thus freed from having to initiate the recomputation manually.