The evaluation of the benefits of an Eco-Driving assistance system is carried out in the urban environment in presence of traffic lights. The traffic evolution is modeled macroscopically with the Urban Variable-Length Model in a variable speed limits framework. Under the assumption of equal boundary flows, the vehicles in a road section dispose themselves according to well defined equilibrium conditions which are dependent on the traveling speed in the free-flow part of the section. Given certain initial traffic conditions, an optimal speed limit for the section can be found in order to drive the system to an efficient equilibrium state. Further analysis of the equilibrium conditions and the stability properties of the system is conducted in this work. The system is proved to be controllable, under the working hypotheses, and a controller is designed to simulate the response of the drivers compliant to the eco-speed advisory. A sub-optimal control strategy is finally proposed also in the case of unequal boundary flows.