Driving in modern cities is getting harder and harder due to the continuously changing road and traffic conditions, binding to navigation systems for successful route planning. Despite navigators are becoming more and more powerful and precise in estimating road and traffic conditions, there is still room for improving their effectiveness in route planning. On the other hand, urban areas, thanks to Information and Communication Technologies, are becoming smarter and smarter, enough to be termed as smart cities since they are able to provide advanced smart services, among which mobility ones. The context of this paper is the integration of such two systems and technologies, merging smart navigation solutions and smart city services to obtain value added services improving route planning effectiveness by achieving a trade-off between the two. To this purpose, a smart navigation system that actively interacts with the smart city infrastructure facilities for route planning is developed. The Smart City Navigation System (SCiNaS) thus implemented provides a solution that, starting from the information obtained by the smart city traffic light management system, is able to “catch” a green wave on the planned route just acting on the vehicle speed by directly interacting with its cruise control. A detailed model of a powertrain c-segment car demonstrated that the proposed solution, SCiNaS, is able to improve both the traveled time and the fuel consumption while reducing the gas emissions. An in depth investigation and comparison between the behavior of a car with the Smart City Navigation System and without the navigation system on an NEDC cycle has been performed.