The invention relates to an adaptive cruise control system for a motor vehicle, having a service brake comprising an electric controller (24), which is equipped to detect the driving data of the motor vehicle and distance data to a preceding vehicle, to compile a movement prediction based on the driving data and the distance data, to influence the state of movement of the motor vehicle by influencing the driving and braking means, and to output a warning signal to a drive of the motor vehicle (10), if the movement prediction indicates that, assuming a predetermined threshold delay (agrenz), an impact probability of an impact with another motor vehicle, with the adaptive cruise control system being activated, exceeds a predetermined impact probability threshold value without any intervention on the part of the drive of the motor vehicle. The invention provides that the electric controller (24) is equipped to detect braking parameters, based on which a maximum brake delay (amax) that can be achieved with the service brakes can be calculated, and to reduce the threshold delay (agrenz), if the maximum brake delay (amax) is below a predetermined delay threshold value.