It is well accepted that vehicular traffic follows a concave flow-density relationship. This relationship is often referred to as the Fundamental Diagram. The purpose of this paper is to develop a dynamic traffic-control formulation that considers the entire Fundamental Diagram. This use of the Fundamental Diagram is especially important for modeling oversaturated traffic. In this paper, traffic is modeled after the cell-transmission model (CTM), which is a convergent numerical approximation to the hydrodynamic model. The author transformed CTM to a set of mixed-integer constraints and subsequently cast the dynamic signal-control problem to a mixed-integer linear program. As a dynamic platform, the formulation is flexible in dealing with dynamic timing plans and traffic patterns. It can derive dynamic as well as fixed timing plans and address preexisting traffic conditions and time-dependent demand patterns. This study produced results to show the benefit of dynamic timing plans and demonstrated that some of the current practices of signal coordination could be further improved. (A)
Abstract