Quality of Service Beyond the Traditional Fundamental Diagram

In the German Highway Capacity Manual (HBS) the design and operation analysis of freeway sections is based on the volume-to-capacity ratio, which is used as a substitute for the average travel speed. For undersaturated flow the travel time can indirectly be calculated from speed-flow diagrams given within the HBS. However, the applicability of speed-flow diagrams is restricted to demand values less than the capacity. A differentiation of oversaturated traffic conditions with a demand beyond the speed-flow diagram is not possible so far. The paper presents approaches for a division of Level of Service F (LOS F) into differentiated degrees (F1 to F4) and proposes corresponding calculation methods. For the estimation of travel times as a function of traffic demand, different traffic flow models and queuing equations are considered. Four standardized methods are described in the paper, differing in the performance measures used. In the first three methods, the peak hour is retained as the analysis interval. In contrast to these concepts, the latter evaluation is based on a 24-hour analysis. This more sophisticated concept allows the consideration of spatial as well as temporal effects. The methods are analyzed and compared in terms of their significance, their sensitivity and the availability of input data. Predominantly, the evaluation methods developed in this research can be applied for assessing the quality of service on congested facilities depending on traffic demand. In the scope of decision making, funds can be spent more efficiently.


  • English

Media Info

  • Media Type: Web
  • Features: Appendices; Figures; References;
  • Pagination: pp 86-106
  • Monograph Title: 75 Years of the Fundamental Diagram for Traffic Flow Theory: Greenshields Symposium
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 01349735
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 12 2011 2:40PM