United States Department of Transportation
i
Assessing and Addressing Deficiencies in the HCM Weaving Segment Analyses
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2021-03-01
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[PDF-4.02 MB]
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Edition:Final Report: 8/1/2018 to 3/14/2021
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Abstract:The Highway Capacity Manual 6th Edition (HCM6) provides methods for the evaluation of freeway segments and freeway facilities including weaving segments. Weaving segments are often critical components of freeway facilities because they can act as bottlenecks. Recent research has questioned the validity of the HCM6 weaving analysis methodology. The main objectives of this research project were to identify, document, and address the major deficiencies in the current HCM6 weaving method through improved modeling of key procedures and their calibration. The research team conducted a literature review to identify and document deficiencies in the procedure. Next, the team collected field data and obtained previously collected data at weaves and developed a new framework for evaluating operations at freeway weaves. This new framework uses the basic segment freeway model and a speed impedance factor that represents the weaving turbulence, which proved to be simpler and more accurate than the models in the HCM6. A model was developed for Type A or ramp weaves, which predicts the average speed of the weaving segment directly without using intermediate models to predict the number of lane changes. It was concluded that the HCM6 model tended to underestimate the speed within the weaving section compared to field data. A sensitivity analysis showed that the new model can predict the speed and capacity for ramp weaves reasonably well.
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