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 such as the Highway Capacity Manual or the German Highway Capacity Manual is based on speed-flow diagrams. More recent investigations, however, have demonstrated that freeway capacity has to be regarded as a random variable. The capacity distribution function represents the probability that a traffic breakdown is dependent 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: Web
  • Features: Figures; References; Tables;
  • Pagination: pp 147-156
  • Monograph Title: 75 Years of the Fundamental Diagram for Traffic Flow Theory: Greenshields Symposium
  • Serial:

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Filing Info

  • Accession Number: 01349724
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 15 2011 8:34AM