A New Scheme for Traffic Flow Estimation and Control With a Two Component Model

Abstract

This paper proposes a control concept to reach high performance traffic flow on cross-country highways under changing demand and constitution of vehicles. For this purpose a two component model of traffic flow is developed which pays special attention to the influence of trucks within the traffic stream. This model characterizes traffic flow by the aggregate variables car-density,total density which relates to cars and trucks and average speed in a road element. Concerning the problem of estimation of these variables the realistic assumption is made that traffic sensors will be located only at distances of several kilometers. A distance between two sensors is called a section which is subdivided into several road elements for the purpose of modeling. A number of such sections is cascaded to form a road unit which is to be kept at high performance by traffic responsive control.A control strategy is developed for this road unit using nonlinear programming and short time prediction. Here on-ramp metering and speed limitations are taken as control inputs. It is demonstrated by the results of simulations that this control concept keeps traffic flow at high performance, while in the uncontrolled case congestion would occur under peak demand. In addition simulations indicate that the two component model yields better control than a one component model when the traffic flow contains a high percentage of trucks. Basic features of a decentralized instrumentation of this concept are outlined.