Research On ITS-Oriented Methods For Traffic Assignment And On-Ramp Control In Freeway Networks

The practice of intelligent management and control in freeway networks urgently calls for the adapted foundation theories and practical technologies. In this dissertation, the modeling of traffic flow, on-ramp control, dynamic traffic assignment in freeway (?) are systematically studied, approaching to intelligent traffic system (ITS). The main works of this paper consist of six parts:(1) By the proper choice of dynamic flow equation and flow-density relation, an improved traffic flow model is put forward, which is suitable for traffic with slight congestion. In this model the effect of downstream congestion on the upstream flow is considered.(2) A traffic flow model with multiple lanes on freeway is proposed aiming at automated highway system (AHS). in which the lane changing and origin-destination (OD) of vehicles are considered. Then this model is applied to on-ramp optimal control. In order to reduce the complexity of the optimal control problem, it is decomposed to a bilevel hierai'chical control problem. The iteration algorithm to the upper layer control problem is put forward, and the simulation of the optimal control problem is given.(3) It is expounded that the intelligent control is an inevitable tendency of traffic control. A fuzzy logic control is applied to on-ramp metering. The parameters of such a fuzzy logic controller can be adapted to an on-ramp. A comparison of computer simulation among pre-time control, optimal control and fuzzy control is given, which shows that the fuzzy control is superior to pre-timed control in both travel time and serving flow.(4) A conception "inductive link resistance (ILR) function" is proposed aiming at the speciality of freeway networks. Using this conception, some multiple objective traffic assignment problems can be converted to optimal problems of the same kind. It is proved that the equilibrium problem of ILR is equal to an optimal control problem. The...