Relationships Between Occupancy and Density Reflecting Average Vehicle Lengths

Abstract

The linearity of the occupancy-density relationship is investigated by studying the relationship mathematically across a wide range of traffic situations as well as by plotting values of both variables on the occupancy-density diagram. The literature does not show general agreement on the linearity of the relationship. The relationship is shown to be practically linear because the nonlinear factor mathematically derived does not have noticeable effects on the linearity of the relationship. However, the plot of both variables on the occupancy-density diagram shows that the relationship is influenced by varying average vehicle lengths and can be interpreted as being either linear or nonlinear. The proportion of long vehicles (trucks) is tested empirically and is shown to have large effects on the linearity of the relationship.

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References

Cassidy

M. J.

, and Coifman

. Relation Among Average Speed, Flow, and Density and Analogous Relation Between Density and Occupancy. In Transportation Research Record 1591, TRB, National Research Council, Washington, D.C., 1997, pp. 1–6.

Edie

L. C.

Traffic Science ( Gazis

D. C.

, ed.), John Wiley and Sons, Inc., New York, 1974, pp. 8–20.

Banks

J. H.

Another Look at A Priori Relationships Among Traffic Flow Characteristics. In Transportation Research Record 1510, TRB, National Research Council, Washington, D.C., 1995, pp. 1–10.

Hall

F. L.

The Relationship Between Occupancy and Density. Transportation Forum, Dec. 1986, pp. 46–52.

Leutzbach

Introduction to the Theory of Traffic Flow. Springer-Verlag, Berlin, Heidelberg, Germany, 1988, pp. 82–83.

Athol

Interdependence of Certain Operational Characteristics Within a Moving Traffic Stream. In Highway Research Record 72, HRB, National Research Council, Washington, D.C., 1965, pp. 58–87.

TLS: Technische Lieferbedingungen fuer Streckenstationen (German Technical Terms of Delivery for Outstations). German Federal Highway Research Institute (BASt), Bergisch Gladbach, Germany, 1997.