Impacts of automated passenger cars on the capacity of a freeway basic section: applicability in the determination of vehicle adjustment factors in mixed traffic

The highway capacity manual (HCM) provides a formula to calculate the heavy vehicle adjustment factor (fHV) as a function of passenger car equivalent factors for the heavy vehicle (ET). However, a significant drawback is that the methodology was established solely based on human-driven passenger car...

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Bibliographic Details
Main Authors: Sia M. Lyimo, Valerian Kwigizile, Jun-Seok Oh, Zachary D. Asher
Format: Article
Language:English
Published: Maximum Academic Press 2023-12-01
Series:Digital Transportation and Safety
Subjects:
Online Access:https://www.maxapress.com/article/doi/10.48130/DTS-2023-0025
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Summary:The highway capacity manual (HCM) provides a formula to calculate the heavy vehicle adjustment factor (fHV) as a function of passenger car equivalent factors for the heavy vehicle (ET). However, a significant drawback is that the methodology was established solely based on human-driven passenger cars (HDPC) and human-driven heavy vehicles (HDHV). Due to automated passenger cars (APCs), a new adjustment factor (fAV) might be expected. This study simulated traffic flows at different percentages of HDHVs and APCs to investigate the impacts of HDHVs and APCs on freeway capacity by analyzing their influence on fHV and fAV values. The simulation determined observed adjustment factors at different percentages of HDHVs and APCs (fobserved). The HCM formula was used to calculate (fHCM). Modifications to the HCM formula are proposed, and vehicle adjustment factors due to HDHVs and APCs were calculated (fproposed). Results showed that, in the presence of APCs, while fobserved and fHCM were statistically significantly different, fobserved and fproposed were statistically equal. Hence, this study recommends using the proposed formula when determining vehicle adjustment factors (fproposed) due to HDHVs and APCs in the traffic stream.
ISSN:2837-7842