In this paper a novel computationally efficient model predictive control (MPC) method for optimizing flows at urban intersections is proposed. Several linear and quadratic MPC approaches have been developed in the literature to reduce the computational complexity of the problem, but without considering the back-propagating waves associated with spillback. As the principal contribution of this work, a linear optimization problem for an MPC approach is formulated, which considers downstream propagating waves linked to free-flow traffic, queuing dynamics, and upstream propagating waves related to spillback (i.e. forward and backward moving waves, respectively). The linear optimization problem is obtained by describing link dynamics using the link transmission model, and aggregating the traffic dynamics to (several) tens of seconds. The performance of the proposed controller is compared with two other existing strategies; a store-and-forward model-based, and a cell transmission model-based approach. The total time spent (TTS) by all the vehicles in the network and the computation time is applied as performance indexes for the evaluation of the control strategies. Simulation results show that including upstream propagating waves results in better controller performance, due to the explicit modeling of the impact of link outflow on the maximum link inflow.

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Empirical and research evidence suggests that traffic-responsive signal control strategies are generally not as efficient in over-saturated traffic conditions characterized by queue spillbacks. Recent studies on (MFD/NFD) have identified a destabilizing gridlock process that arises in congested networks which precludes efficient operation. The MFD has also been used to develop urban traffic control solutions (e.g. perimeter or gating control) to avoid congestion. The purpose of this paper is to explore the benefits of combining gating with locally adaptive traffic signals through micro-simulation of the Chania, Greece traffic network. Two adaptive traffic signal strategies are considered with the perimeter control strategy. The results of the combined gating/adaptive signal control scheme are compared to gating under fixed traffic signals and the implementation of adaptive signals only. The convincing outcome of this simulation study motivates the real-field implementation of gating/perimeter control in the cities, without even changing the existing adaptive control strategies.@en