FREEWAY SPEED-FLOW-CONCENTRATION RELATIONSHIPS: MORE EVIDENCE AND INTERPRETATIONS (WITH DISCUSSION AND CLOSURE)
In this paper, recent Canadian work challenging long-held theories about speed-flow-concentration relationships in freeway traffic is verified and extended using data from San Diego. Major conclusions of these studies regarding near-constant free-flow speeds and flow-concentration relationships resembling an inverted V are confirmed; other past findings related to the effect of queuing on downstream free-flow speeds and the effect of secondary bottlenecks on flow-concentration relationships are not confirmed. When data are averaged across all lanes (both upstream and downstream of a bottleneck), speed-flow and flow-concentration relationships are found to be consistent with those predicted by queuing and shock wave theory. The functioning of the bottleneck studied is more complicated than had been assumed, however, and this creates further problems in the interpretation of the data. Finally, the inverted-V model of the flow-concentration relationship is shown to imply a simple and plausible model of driver behavior in which speeds and spacings are adjusted to keep the average front-to-back time gaps approximately constant until some desired maximum speed is reached.
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Availability:
- Find a library where document is available. Order URL: http://worldcat.org/isbn/0309049520
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Supplemental Notes:
- This paper appears in Transportation Research Record No. 1225, Highway Capacity, Flow Measurement, and Theory. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
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Authors:
- Banks, James H
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Discussers:
- Furth, Peter G
- Publication Date: 1989
Media Info
- Features: Figures; References;
- Pagination: p. 53-60
- Monograph Title: Highway capacity, flow measurement, and theory
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Serial:
- Transportation Research Record
- Issue Number: 1225
- Publisher: Transportation Research Board
- ISSN: 0361-1981
Subject/Index Terms
- TRT Terms: Bottlenecks; Freeways; Highway traffic; Queuing; Shock waves; Traffic density; Traffic flow; Traffic simulation; Traffic speed; Vehicle spacing
- Uncontrolled Terms: Relationships
- Old TRIS Terms: Freeway traffic
- Subject Areas: Highways; Operations and Traffic Management; I71: Traffic Theory;
Filing Info
- Accession Number: 00494966
- Record Type: Publication
- ISBN: 0309049520
- Files: TRIS, TRB
- Created Date: Jun 30 1990 12:00AM