Development of a methodology for measuring delay-based passenger car equivalent for heavy vehicles at signalized intersections
Zhao, Weixiong
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https://hdl.handle.net/2142/19971
Description
Title
Development of a methodology for measuring delay-based passenger car equivalent for heavy vehicles at signalized intersections
Author(s)
Zhao, Weixiong
Issue Date
1996
Doctoral Committee Chair(s)
Benekohal, Rahim F.
Department of Study
Civil and Environmental Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Transportation
Language
eng
Abstract
The majority of the current methods for measuring passenger car equivalent (PCE) for heavy vehicles at signalized intersections are based on headway concepts, and are mainly focused on adjusting the ideal saturation flow rate. They do not reflect the total effect of heavy vehicles on delay. The constant PCE value, which is independent of traffic volume and percentage of heavy vehicles, is inappropriate in capacity analysis when delay is considered. Among other analysis procedures, the 1985 Highway Capacity Manual (HCM) and the 1994 HCM were found to be deficient for estimating the effects of heavy vehicles.
This research introduces a new method for measuring PCE for heavy vehicles at signalized intersections: Delay-Based PCE (D-PCE). Effects of heavy vehicles are examined based on their additional induced vehicular delay. Both field analysis and simulation analysis approaches for measuring Delay-Based PCE are presented. A new set of PCE values for two heavy vehicle types, single unit truck and combination truck, are recommended for use.
Field analysis procedures are applied to the field data collected at seven separate signalized approaches. Delay effects of specific heavy vehicles in queue are examined in conjunction with their position in the queue and the number of vehicles queued behind them. A simulation model is presented to estimate D-PCE value under wide range of traffic volume and percentage of heavy vehicles.
Signal settings, including cycle length and green time, are found to have no significant effect on Delay-Based PCE values when the traffic is undersaturated. D-PCE values is highly correlated with traffic volume and to some degree with the percentage of heavy vehicles. D-PCE values increase as the traffic volume gets heavier, and as the percentage of heavy vehicles gets greater. The general equation for estimating D-PCE values can be described as a linear relationship with the traffic volume and the reciprocal of percentage of heavy vehicles.
Compared with the Delay-Based PCE, the use of 1.5 and 2.0 in HCM overestimates the capacity reduction for some traffic conditions, and underestimates it for other conditions, depending on the traffic volume and percentage of heavy vehicles.
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