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Some Properties of Flows at Freeway Bottlenecks

Listed author(s):
  • Lei Zhang
  • David Levinson


    (Nexus (Networks, Economics, and Urban Systems) Research Group, Department of Civil Engineering, University of Minnesota)

Capacity of a freeway segment should only be measured when it is an active bottleneck. The properties of flows at active freeway bottlenecks bear on both the definition of capacity and the procedure of capacity analysis. Past studies have examined the flow features at bottlenecks on several freeways in Toronto, Ontario, and San Diego, California. This study examined twentyseven active bottlenecks in the Twin Cities metro area, Minnesota, for a seven-week period. The analysis focuses on the properties of pre-queue transition flows (PQF) and queue discharge flows (QDF) averaged across various time intervals (thirty-second, daily average, and long-run average). It is found that the percentage flows drop after upstream queues form at all studied bottlenecks range from 2 percent to 11 percent. The 30-second QDFs display high variation and should not be assumed to be constant. The daily average QDFs at each studied bottleneck follows a normal distribution based on two normality tests and visual inspection of the normal probability plot. Results also suggest that the long-run average QDFs (mean 2016 pc/ln/hr) and PQFs (mean 2124 pc/ln/hr) are both normally distributed. The implication of these empirical findings on capacity estimation is also discussed.

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Paper provided by University of Minnesota: Nexus Research Group in its series Working Papers with number 200403.

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Date of creation: 2004
Publication status: Published in Journal of the Transportation Research Board No. 1883 122-131.
Handle: RePEc:nex:wpaper:bottleneckproperties
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Dept. of Civil Engineering, 500 Pillsbury Drive SE, Minneapolis, MN 55455

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  1. Zhang, Lei & Levinson, David, 2010. "Ramp metering and freeway bottleneck capacity," Transportation Research Part A: Policy and Practice, Elsevier, vol. 44(4), pages 218-235, May.
  2. Cassidy, Michael J. & Bertini, Robert L., 1999. "Some traffic features at freeway bottlenecks," Transportation Research Part B: Methodological, Elsevier, vol. 33(1), pages 25-42, February.
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