A module for determining speed set-point values vref for a vehicle's control systems includes an input unit configured for input, e.g. by the vehicle's driver, of a reference speed vset which is the speed desired by the driver for the vehicle. A horizon unit is configured for determining a horizon by means of received position data and map data of an itinerary made up of route segments with at least one characteristic for each segment. A processor unit is configured for calculating vref across the horizon according to rules pertaining to categories in which segments within the horizon are placed, so that vref is within a range bounded by vmin, and vmax, where vmin≦̸vset≦̸vmax. The processor unit is further configured for determining a control signal with control parameters for the vehicle's automatic gear change control unit, based on one or more vehicle-specific values and a calculated speed set-point value vref.