the case of complete consumption or in the case of consumption up to the minimum residual reserve the edge 44 is determined here as a function of the section of road for which reason it has an irregular profile on the roadmap 30 an edge 46 of the plateau plane 40 can be determined on the basis of a second average consumption value by using a plateau as a vertically offset region 36 the advantage is obtained here that in the simplest case the region 42 which drops away can already be determined on the basis of only two average consumption values fig3 shows a display of the roadmap 30 in which the range indicator comprises a vertically offset region 36 u2032 in the form of a bulge or elevated area with a rounded off region 42 u2032 which drops away representing the vertically offset region 36 u2032 in the form of a bulge provides the advantage that in the region 42 u2032 which drops away more precise information can be provided about the probability of a certain location still being able to be reached with the remaining quantity of energy fig4 shows the roadmap 30 for the case in which the range indication is provided by a vertically offset region 36 u2033 in the form of a depression or a valley this representation can be followed intuitively by the driver since he is given the impression that it.