Missouri Work Zone Capacity: Results of Field Data Analysis
This report presents the results of work zone field data analyzed on interstate highways in Missouri to determine the mean breakdown and queue-discharge flow rates as measures of capacity. Several days of traffic data collected at a work zone near Pacific, Missouri with a speed limit of 50 mph were analyzed in both the eastbound and westbound directions. As a result, a total of eleven breakdown events were identified using average speed profiles. The traffic flows prior to and after the onset of congestion were studied. Breakdown flow rates ranged between 1194 to 1404 vehicles per hour per lane (vphpl), with an average of 1295 vphpl, and a mean queue discharge rate of 1072 vphpl was determined. Mean queue discharge, as used by the Highway Capacity Manual 2000 (HCM), in terms of passenger car per hour per lane (pcphpl) was found to be 1199, well below the HCM’s average capacity of 1600 pcphpl . This reduced capacity found at the site is attributable mainly to narrower lane width and higher percentage of heavy vehicles, around 25%, in the traffic stream. The difference found between mean breakdown flow (1295 vphpl) and queue-discharge flow (1072 vphpl) has been observed widely, and is due to reduced traffic flow once traffic breaks down and queues start to form. The Missouri Department of Transportation currently uses a spreadsheet for work zone planning applications that assumes the same values of breakdown and mean queue discharge flow rates. This study proposes that breakdown flow rates should be used to forecast the onset of congestion, whereas mean queue discharge flow rates should be used to estimate delays under congested conditions. Hence, it is recommended that the spreadsheet be refined accordingly.
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Supplemental Notes:
- This report was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
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Corporate Authors:
Mid-America Transportation Center
University of Nebraska-Lincoln
2200 Vine Street, PO Box 830851
Lincoln, NE United States 68583-0851Research and Innovative Technology Administration
1200 New Jersey Avenue, SE
Washington, DC United States 20590 -
Authors:
- Bham, Ghulam H
- Khazraee, S Hadi
- Publication Date: 2011-6
Language
- English
Media Info
- Media Type: Web
- Edition: Final Report
- Features: Appendices; Figures; Photos; References; Tables;
- Pagination: 61p
Subject/Index Terms
- TRT Terms: Field studies; Highway capacity; Traffic congestion; Traffic flow rate; Traffic queuing; Traffic volume; Work zones
- Uncontrolled Terms: Queue discharge rate; Traffic flow breakdown
- Geographic Terms: Missouri
- Subject Areas: Highways; Operations and Traffic Management; I73: Traffic Control;
Filing Info
- Accession Number: 01449701
- Record Type: Publication
- Report/Paper Numbers: 25-1121-0001-118, MATC-MST: 118
- Files: UTC, NTL, TRIS, ATRI, USDOT
- Created Date: Oct 22 2012 9:13AM