EMME/2 Support Center
Haldenstrasse 16, CH-2558 Aegerten, Switzerland
October 1989
(Appendices 1 and 2 added August 1997)
This paper (without the appendices) also appeared in
Transportation Science, Vol 24., No. 2, 1990.
Abstract:
The widely used BPR volume-delay functions have some inherent drawbacks. A set of conditions is developed which a ``well behaved'' volume delay function should satisfy. This leads to the definition of a new class of functions named conical volume-delay functions , due to their geometrical interpretation as hyperbolic conical sections. It is shown that these functions satisfy all conditions set forth and, thus, constitute a viable alternative to the BPR type functions.
A PDF version of this document is also available.
Contents
- Introduction
- Requirements for a Well Behaved Congestion Function
- Conical Congestion Functions
- Conclusions
- References
- Appendix 1: Marginal Cost Functions
- Appendix 2: Efficient Coding of Conical Functions in EMME/2
Introduction
In most traffic assignment methods, the effect of road capacity on travel times is specified by means of volume-delay functions t(v) which used to express the travel time (or cost) on a road link as a function of the traffic volume v. Usually these functions are expressed as the product of the free flow time multiplied by a normalized congestion function f(x)
