SPEED, VOLUME, AND DENSITY RELATIONSHIPS
ANALYSIS OF FIELD DATA FOR TWO SITES SHOWS THAT THERE SEEMS TO BE AN EXPONENTIAL RELATIONASHIP BETWEEN THE SPACE MEAN SPEED OF TRAFFIC AND ITS DENSITY. FAMILIES OF CURVES, EXPRESSING RELATIONSHIPS BETWEEN TRAVEL TIME AND DENSITY, SPEED AND DENSITY, TRAVEL TIME AND VOLUME AND SPEED AND VOLUME AND SPEED AND VOLUME IN TERMS OF PROBABILITIES ARE PRODUCED FOR THE TWO STUDY SITES. THE VALIDITY OF THE EXPONENTIAL SPEED-DENSITY MODEL IS EXAMINED. IT IS FOUND THAT IT CANNOT BE APPLIED TO EXPRESSWAY-TYPE FACILITIES, ALTHOUGH IT SEEMS TO HAVE APPLICATION TO LOWER TYPE ROADWAYS. A GENERALIZED SPEED-VOLUME DIAGRAM IS INTRODUCED, CONSISTING OF THREE SEPARATE ZONES: A ZONE OF NORMAL FLOW, A ZONE OF UNSTABLE FLOW AND A ZONE OF FORCED FLOW, EACH ZONE BEING SPECIFIED IN TERMS OF PROBABILITIES. THE DIAGRAM IS CHECKED AGAINST AVAILABLE SPEED-VOLUME DATA FOR SEVERAL DIFFERENT FACILITIES, AND IS COMPARED WITH EXISTING FLOW MODELS. FOR CERTAIN LOWER TYPE FACILITIES THERE APPEARS TO BE AN EXPONENTIAL RELATIONSHIP BETWEEN THE SPACE MEAN SPEED OF TRAFFIC AND ITS DENSITY. THE SPEED-VOLUME DIAGRAM IS CONSISTENT AND CAN BE RECONCILED WITH THE MODELS OF GREENSHIELDS, NORMANN AND GREENBERG. THE CONCEPT OF THREE DISTINCT FLOW ZONES, IF DEVELOPED FURTHER, COULD LEAD TO A CLEARER UNDERSTANDING OF THE THEORY OF TRAFFIC FLOW.
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Supplemental Notes:
- pp 141-188, 23 FIG, 3 TAB
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Corporate Authors:
Pennsylvania State University, University Park
Bureau of Highway Traffic
University Park, PA United States 16802 -
Authors:
- Underwood, R T
- Publication Date: 0
Subject/Index Terms
- TRT Terms: Analysis; Mathematical models; Probability theory; Traffic; Traffic density; Traffic flow theory; Traffic simulation; Traffic speed; Traffic volume; Travel time
- Uncontrolled Terms: Traffic analysis
- Subject Areas: Data and Information Technology; Highways; Operations and Traffic Management;
Filing Info
- Accession Number: 00227130
- Record Type: Publication
- Files: TRIS
- Created Date: Aug 13 2004 6:47PM