Perimeter Control and Route Guidance of Multi-Region MFD Systems With Boundary Queues Using Colored Petri Nets

Abstract

Perimeter control based on Macroscopic Fundamental Diagram (MFD) aims to meter the number of transferring vehicles at the periphery of the protected urban region in order to obtain the desired number of vehicles in that region. The advantage of perimeter control is less computational effort, while its drawback is that it may create long queues and delays at the perimeter of the controlled area. For capturing boundary queue dynamics, an enhanced accumulation-based MFD model is proposed using colored Petri Nets by considering transfer flows, boundary queues and travel delays simultaneously. The gated intersections and related road segments on the border of a protected region are modeled as so-called boundary buffers. Based on the enhanced MFD model, anintegrated perimeter control framework is proposed with consideration of travel time and queuing time in buffers. In this framework, the controllers between peripheral and protected region are optimized using model predictive control theory. Then, internal flow controllers are adopted to homogenize traffic density among subregions, and route guidance is also used to balance the number of queuing vehicles among boundary buffers. Simulation results verify the effectiveness of the proposed integrated perimeter control. Furthermore, the impacts of buffer storage capacity on region heterogeneity and trip completion rates are also investigated in this paper. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —It is challenging to manage traffic congestion in large-scale urban network. Perimeter control provides an accumulation-based methodology with consideration of the existing correlation between traffic density and flow, which is known as MFD. For practical application, the efficiency as well asweakness of potential perimeter control strategies need to be evaluated and improved using customized traffic simulations. Accumulation-based traffic model using Petri Nets is introduced to serve for perimeter control, in which the intersections and road segments on the boundary of each pair of adjacent subregions are modeled as a boundary buffer. Both perimeter control and route guidance are integrated in the proposed control framework considering the queuing vehicles in the boundary buffers. Moreover, the effect of buffer storage capacity on network performances is tested, which is the essential for traffic engineers to design and implement management measures in practice.