Defining, Measuring, and Modeling Capacity for the Highway Capacity Manual
The highway capacity manual (HCM) is the publication used most often to estimate capacity. Field measurements in previous research have shown that the capacities at several freeway bottlenecks are noticeably lower than the values recommended in the HCM, by an order of a few hundred vehicles per lane. In addition, several articles have shown that maximum freeway throughput may differ between undersaturated and oversaturated conditions. This paper assembles capacity flows before and after the initiation of oversaturation, discusses recommended definitions of capacity, and provides capacity values and capacity prediction models for various types of freeway segments. It is recommended to define prebreakdown capacity as the 85th percentile of the 15-min average prebreakdown flow and the postbreakdown capacity as the 85th percentile of the 15-min average discharge flow. A clear drop in throughput between prebreakdown and discharge capacity values was observed. The paper concludes by providing recommended capacity values as a function of the number of lanes and the segment type. These values are significantly lower than those recommended in the HCM for basic freeway segments.
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Availability:
- Find a library where document is available. Order URL: http://worldcat.org/issn/24732907
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Supplemental Notes:
- © 2016 American Society of Civil Engineers.
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Authors:
- Kondyli, Alexandra
- St. George, Bryan
- Elefteriadou, Lily
- Bonyani, Gina
- Publication Date: 2016-11
Language
- English
Media Info
- Media Type: Web
- Features: References;
- Pagination: 04016014
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Serial:
- Journal of Transportation Engineering, Part A: Systems
- Volume: 143
- Issue Number: 3
- Publisher: American Society of Civil Engineers
- ISSN: 2473-2907
- EISSN: 2473-2893
- Serial URL: http://ascelibrary.org/journal/jtepbs
Subject/Index Terms
- TRT Terms: 85th percentile speed; Bottlenecks; Highway capacity; Highway design; Traffic flow; Traffic oversaturation
- Identifier Terms: Highway Capacity Manual
- Subject Areas: Design; Highways; Operations and Traffic Management;
Filing Info
- Accession Number: 01627850
- Record Type: Publication
- Files: TRIS, ASCE
- Created Date: Feb 28 2017 9:11AM