Capacity Analysis Framework for Freeway Ramp Weaves
Publication: Journal of Transportation Engineering, Part A: Systems
Volume 147, Issue 12
Abstract
The Highway Capacity Manual 6th Edition (HCM6) provides methods for evaluating freeway segments and facilities, including weaving segments. Recent research has cast doubt on the validity of some elements of the HCM6 weaving methodology. The core objectives of this research were to identify, document, and address key deficiencies in the current HCM6 weaving method through an improved modeling framework and its calibration. This new framework starts with the basic freeway segment speed model and incorporates a speed impedance factor that represents the effect of weaving turbulence. This approach proved to be simpler and more accurate than the current HCM6 models when tested with field measurements. The speed and capacity prediction models were developed for ramp weaves, avoiding the use of intermediate models to predict the number of lane changes and speeds by weaving maneuvers. The study found that the new speed prediction model is more accurate, while the HCM6 model underestimates the speed within the weaving section compared to field data. A sensitivity analysis showed that the new speed and capacity models behaved properly to changes in segment length, weaving flows, and overall demand. The proposed framework is applicable to the analysis of merge and diverge segments and can ensure continuity in predicting the operational performance across different freeway segment types.
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Data Availability Statement
Some or all data, models, or code generated or used during the study are available from the corresponding author by request.
Acknowledgments
This material is based upon work supported by the regional Southeastern Transportation Research and Innovation, Development and Education (STRIDE) center project (69A3551747104). Assessing and addressing deficiencies in the HCM weaving segment analyses.
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Journal of Transportation Engineering, Part A: Systems
Volume 147 • Issue 12 • December 2021
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Nov 9, 2020
Accepted: Jul 7, 2021
Published online: Sep 23, 2021
Published in print: Dec 1, 2021
Discussion open until: Feb 23, 2022
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