A method and device for displaying road segments are provided. The method uses a map data base storing information on a road network in a road vector data format. Additional parameter values are stored for a subset of road segments. Information on a direction vector and the parameter value for a road segment are retrieved. Based on the parameter value, it is determined whether the road segment exhibits a variation in shape as a function of position along its direction vector. A graphical representation of the road segment is generated based on the retrieved parameter value and the direction vector.