Variable Speed Limits Control in an Urban Road Network to Reduce Environmental Impact of Traffic

The problem of improving traffic sustainability and traffic efficiency in an urban road network, by implementing variable speed limits (VSL), is addressed in this paper. A nonlinear model predictive control (NMPC) design based on a first-order macroscopic traffic flow model is proposed for the speed limits optimization in each segment of the road network. Simulation results show the effectiveness of the proposed control approach, compared to reference cases in which the speed limits are constantly set to 30 km/h or 50 km/h. In the particular case of congested traffic conditions, the controller is capable of reducing both energy consumption and travel time, without delaying users waiting at the network boundaries.