This paper proposes a design method for cruise control systems via reference speed optimization considering road and traffic information. During the optimization several factors are considered such as road inclinations, intersections, traffic lights, preceding vehicles, speed limits, engine emissions and traveling time. The purpose of speed design is to reduce the longitudinal energy, fuel consumption and engine emissions in such a way that the travel time does not increase significantly. The information package of traffic lights also infuences the design process. The signals from the road and traffic are handled jointly with the dynamic equations of the vehicle and built into the control design of reference speed. A robust control is designed, which is able to take into consideration both disturbances and uncertainties. The method is illustrated through simulation examples.