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Comparing the speed-flow relationship for motorways with new data from the M6


  • Smith, W. Spencer
  • Hall, Fred L.
  • Montgomery, Frank O.


This paper draws on data collected in March 1993 from the M6 motorway north of Birmingham, England, to discuss the speed-flow relationships used in cost benefit analysis. Piece-wise linear functions have been fitted to the M6 data, and are then compared to the relationships in the U.K. Cost Benefit Analysis Manual (COBA9: U.K. Department of Transport, 1981), and the U.S. Highway Capacity Manual (HCM: U.S. Transpn Res Bd, 1994). The results provide clear support for the value of 1200 v/h/l used in COBA9 as the flow at which speeds start to decrease more rapidly, but in other respects the results differ from values in both COBA9 and the HCM. In comparison with the observed data, COBA9 estimates: a lower speed at a flow of 1200 v/h/l; a steeper slope at higher flows; a higher capacity flow; and a lower speed at capacity. Equivalently, HCM estimates: a gentler slope at higher flows; a higher capacity flow; and a higher speed at capacity. Thus the high-flow data fall somewhere between the COBA9 and HCM estimates.

Suggested Citation

  • Smith, W. Spencer & Hall, Fred L. & Montgomery, Frank O., 1996. "Comparing the speed-flow relationship for motorways with new data from the M6," Transportation Research Part A: Policy and Practice, Elsevier, vol. 30(2), pages 89-101, March.
  • Handle: RePEc:eee:transa:v:30:y:1996:i:2:p:89-101

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    Cited by:

    1. Coifman, Benjamin A. & Mallika, Ramachandran, 2007. "Distributed surveillance on freeways emphasizing incident detection and verification," Transportation Research Part A: Policy and Practice, Elsevier, vol. 41(8), pages 750-767, October.
    2. Koetse, M.J. & Rouwendal, J., 2008. "Transport and welfare consequences of infrastructure investment : a case study for the Betuweroute," Serie Research Memoranda 0012, VU University Amsterdam, Faculty of Economics, Business Administration and Econometrics.
    3. Erik T. Verhoef & Jan Rouwendal, 2004. "Pricing, Capacity Choice, and Financing in Transportation Networks," Journal of Regional Science, Wiley Blackwell, vol. 44(3), pages 405-435.
    4. Koetse, Mark J. & Rouwendal, Jan, 2010. "Rail investment and port competition: a case study for the Betuweroute," European Transport \ Trasporti Europei, ISTIEE, Institute for the Study of Transport within the European Economic Integration, issue 44, pages 57-75.
    5. repec:eee:touman:v:33:y:2012:i:2:p:466-479 is not listed on IDEAS

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