Empirical Relation Between Stochastic Capacities and Capacities Obtained from the Speed-Flow Diagram

In conventional procedures for the assessment of traffic flow quality, the capacity of highway facilities is treated as a constant value. For freeways, the derivation of design capacities given in guidelines like the Highway Capacity Manual (HCM) or the German HBS is based on speed-flow diagrams. More recent investigations, however, demonstrated that freeway capacity has to be regarded as a random variable. The capacity distribution function represents the probability of a traffic breakdown in dependence on the flow rate. The objective of the paper is to compare stochastic capacities with conventional capacity values. For a considerable number of data samples from freeway sections in Germany, the breakdown probability that corresponds to the capacity obtained from the speed-flow diagram is determined. In conclusion, suitable breakdown probabilities that could be used for the definition of design capacities are derived.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 12p
  • Monograph Title: Symposium on the Fundamental Diagram: 75 Years (Greenshields 75 Symposium), July 8-10, 2008, Woods Hole, MA. Preprints

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Filing Info

  • Accession Number: 01109354
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 22 2008 11:30AM