A DETERMINISTIC TRAFFIC FLOW MODEL FOR THE TWO-REGIME APPROACH

Abstract

In recent years it has been shown that the relationship between flow and concentration is probably not continuous under maximum flow conditions. A previous paper (2) concerned with the evaluation of traffic flow models examined the steady-state equations derived from the generalized car-following model designed by Gazis, Herman, and Rothery. These macroscopic relationships were subjected to 45 data sets, in which most of the data were from freeway lanes, for both single- and two-regime models. From the results of these data sets, the deficiencies of the various models using the two-regime approach were identified and the need for investigating a new two-regime approach was stressed. This paper discusses the development of a new model at both the microscopic and macroscopic levels. The steady-state equation derived from the new model is analytically evaluated by using 45 data sets. The model, based on a new car-following sensitivity component, shows that the free- flow regime and the congested-flow regime are fairly well adapted to convexity and concavity properties respectively in a speed-concentration relationship. By using the analysis of driver performance as a sensitivity measurement, model parameters are defined and evaluated. In addition, the two flow regimes are incorporated by means of breakpoint evaluation procedures. In the light of two-regime phenomena the new steady-state formulation may be superior to the steady-state equations derived from the generalized car-following model, particularly in simplicity and clarity.