An adaptive cruise control system for a motor vehicle includes a service brake comprising an electronic controller programmed/configured to detect driving data of the vehicle and distance data to a preceding vehicle, to calculate a movement prediction based on the driving and distance data, to influence the movement of the vehicle by influencing driving and braking, and to output a warning signal to the vehicle driver if the prediction indicates that, assuming a predetermined limiting braking retardation, a probability of an impact with another vehicle, with the adaptive cruise control system being activated, exceeds a predetermined impact probability threshold value without any intervention on the part of the driver. The controller is configured to detect braking parameters, based on which a maximum braking retardation that can be achieved with the service brakes can be calculated, and to reduce the limiting retardation, if the maximum retardation is below a predetermined value.