Proposed Equations for HCM-6 Passenger Car Equivalent Values

Antonio Hurtado-Beltran, Laurence R. Rilett

Research output: Contribution to journalArticlepeer-review


In the current version of the Highway Capacity Manual (HCM-6), the equal capacity passenger car equivalency (EC-PCE) method is used to account for the effect of trucks for capacity analyses. The EC-PCEs for freeway segments were estimated using a microsimulation-based methodology where a nonlinear regression model (NLRM) with 15 model parameters was used to develop capacity adjustment factor (CAF) models using the microsimulation data as input. The objective of this paper is to introduce a simpler nonlinear regression model with 6 model parameters that can be used for the estimation of CAF values and EC-PCE values for freeway and multilane highway segments. It was found that the proposed model can readily substitute the original model with little loss in fidelity. The CAF formulae developed in this paper can be used to calculate EC-PCE values directly, obviating the need for the HCM-6 EC-PCE tables. Equally important, the simpler models provide the user with a better understanding of the trade-offs between capacity, CAF, and EC-PCE values and the parameters that affect them.

Original languageEnglish (US)
Article number04021104
JournalJournal of Transportation Engineering Part A: Systems
Issue number1
StatePublished - Jan 1 2022
Externally publishedYes


  • Capacity
  • Capacity adjustment factors (CAF)
  • Freeway
  • Highway capacity manual (HCM)
  • Passenger car equivalency (PCE)
  • Regression

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Transportation


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