Monitoring Signalized Urban Networks: Dynamic Equilibrium-Free Model Based on a Discrete-Time Optimal Control Formulation

Abstract

Monitoring traffic operations in a detailed manner and at the network level is a fundamental component in optimal traffic systems control. Especially in the case of urban signalized networks, accurate and reliable systems monitoring is essential for applying a wide range of control strategies, mechanisms, and concepts, such as information provision, signal control, and optimal routing. This paper presents a discrete-time optimal control scheme for monitoring urban signalized networks, augmenting real-time traffic information with a dynamic traffic model. A detailed representation of network traffic based on the cell transmission model was dynamically calibrated with a quasi-Newton nonlinear process that could tackle optimization cases of noncontinuous variables by approximating derivatives and performing a line search. An alternative network loading assumption was tested. The loading process covering all network links’ flows relied not on complex dynamic equilibrium assumptions that could infer unnecessary estimation inaccuracies but on the combined estimation of entry flows and turning proportions at each intersection. Results from the application of the proposed framework on a realistic urban network provide encouraging evidence of its value for monitoring realistic urban traffic systems.