Impact of Capacity Definition on the HCM-6 Passenger Car Equivalent Values
Publication: Journal of Transportation Engineering, Part A: Systems
Volume 148, Issue 7
Abstract
In the current version (Version 6) of the Highway Capacity Manual (HCM), equal-capacity passenger car equivalencies (EC-PCEs) are used to account for the effect of trucks for capacity analyses. The EC-PCEs for freeway segments were estimated using a microsimulation-based methodology in which the capacity of different traffic scenarios was modeled. However, the current EC-PCEs were estimated under assumptions atypical of past HCM releases, including a new definition of capacity and a new data aggregation level. It is important to assess to what extent these assumptions may affect the passenger car equivalencies (PCE) values published in the HCM-6. Consequently, this paper compares the HCM-6 PCEs, and associated capacity adjustment factors (CAF), with values developed using the HCM-6 EC-PCE methodology with historic HCM assumptions. It was found the EC-PCE values from the proposed approach were, on average, 18.2% greater than those published in the HCM-6. This finding suggests the values published in the HCM-6 could underestimate the effect of trucks in capacity and level of service analyses.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
The authors would like to thank the Nebraska Transportation Center and Universidad Michoacana de San Nicolás de Hidalgo for providing the necessary technical tools used in this research. We would also thank Dr. George List and his colleagues at North Carolina State University for their advice on the 2016 HCM EC-PCE estimation methodology and the background information they provided. It is greatly appreciated. In addition, the authors would like to acknowledge the Fulbright foundation who supported Dr. Hurtado-Beltran’s Ph.D. work at the University of Nebraska-Lincoln. The contents of this paper reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented herein and are not necessarily representative of any group or agency.
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Published In
Journal of Transportation Engineering, Part A: Systems
Volume 148 • Issue 7 • July 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Jan 15, 2021
Accepted: Feb 24, 2022
Published online: Apr 27, 2022
Published in print: Jul 1, 2022
Discussion open until: Sep 27, 2022
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