01473350

Component

https://doi.org/10.3141/2395-03

http://scholar.google.com...hail&publication_year=2013

The Highway Capacity Manual (HCM) methodology provides a fast and reliable approach for the analysis of freeway traffic operations; research is ongoing to add a reliability analysis component to the method. Several key methodological enhancements are needed to make the method ready for reliability analysis; these enhancements are described and illustrated in this paper and include (a) the incorporation of the drop in capacity in the queue discharge flow compared with the prebreakdown flow; (b) the addition of a speed adjustment factor (SAF) as a new calibration factor for the modeling of nonrecurrent congestion sources, such as weather and incidents; (c) the explicit incorporation of SAFs and capacity adjustment factors (CAFs) into the HCM methodologies for merge, diverge, and weave segments; (d) the development of new SAF and CAF default values for freeways; and (e) the addition of new congestion performance measures. The enhancements overcome key limitations in the existing HCM 2010 freeway facility method, which assumes a fixed capacity throughout undersaturated and congested regimes, ignores the free-flow speed–reducing effects of inclement weather, and treats weave and merge–diverge segments as basic freeway segments for CAFs less than 1.0. In addition to the existing performance measures generated by the computational engine, some new output variables are proposed: the travel time index and a denied entry queue length measure. The various enhancements are illustrated with computational examples, and a discussion is offered as to the effects of the enhancements on conventional freeway facilities analysis, even without the evaluation of reliability.

01517906

13-0600

English

pp 21–30

2013

Transportation Research Record: Journal of the Transportation Research Board

9780309287180

Print

Figures (3) ; References (29) ; Tables (5)

Free flow speeds; Freeway operations; Freeways; Methodology; Reliability (Statistics); Travel time

Highway Capacity Manual 2010

Data and Information Technology; Highways; Operations and Traffic Management; Planning and Forecasting; I71: Traffic Theory; I73: Traffic Control

TRIS, TRB, ATRI

Feb 5 2013 12:14PM

• Assessment of Design Hours for Freeways
• Breakdown Maturity Phenomenon at Wisconsin Freeway Bottlenecks
• Complete Enough for Complete Streets? Sensitivity Testing of Multimodal Level of Service in the Highway Capacity Manual
• Development of an Oversaturated Speed–Flow Model Based on the Highway Capacity Manual
• Dynamic Modeling of VISSIM’s Critical Gap Parameter at Unsignalized Intersections
• Estimation of Incident Propensity for Reliability Analysis in the Highway Capacity Manual
• Lane-Based Breakdown Identification at Diverge Sections for Breakdown Probability Modeling
• Observations and Analysis of Multistep-Approach Lane Changes at Expressway Merge Bottlenecks in Shanghai, China
• Operational Effectiveness of Passing Zones Depending on Length and Traffic Volume
• Quantifying Measurement Error in Arterial Travel Times Measured by Bluetooth Detectors
• Rethinking the Driver Population Factor: Examination of Freeways in California
• Revised Version of the Automobile Level-of-Service Methodology for Urban Streets in the Highway Capacity Manual 2010
• Toward a Capacity Analysis Procedure for Nonstandard Two-Way Stop-Controlled Intersections
• Volume-to-Capacity Estimation of Signalized Road Networks for Metropolitan Transportation Planning