Citation

Ceder A. Transp. Res. Rec. 1976; 567: 16-30.

Copyright

(Copyright © 1976, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

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.