Citation

Lee J, Yu JC. Highw. Res. Rec. 1973; 456: 40-49.

Copyright

(Copyright © 1973, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

The objective of this paper is to establish an acceptable parameter for the internal energy of traffic flow so that further exploration of traffic dynamics can be pursued. Through a boundary condition analysis of traffic flows, it has been found that the currently suggested "acceleration noise" is not a good measure of the internal energy.

RESULTS of a theoretical analysis of analogous compressible fluid conditions indicate that, if the kinetic energy of a traffic stream is defined as (alpha) (k) (u sq), the principle of conservation of energy will not apply. This is because, when density is used instead of total number of vehicles, the system is not confined; thus energy will not be conserved. The compressible fluid analogy further represent the internal energy of traffic flows. Because the accuracy of this compressible fluid analogy is questionable, the term pi((ki/ko)-1) is not directly applicable to traffic flows. Instead, an empirical approach is used in the search for a suitable internal energy parameter. Aerial photographic traffic data were used in this effort. Four vehicle-interaction-related parameters were analyzed. One of the parameters tested, the coefficient of variation of speed, not only has exhibited a variational pattern that agrees with that of the pi((ki/ko)-1) but also satisfies the boundary condition requirements. It is, therefore, proposed as a suitable measure of the internal energy of traffic flow.

Language: en

Keywords

TRAFFIC SURVEYS; PHOTOGRAMMETRY