Passenger Car Equivalents for Highway Cost Allocation

Abstract

Existing passenger car equivalent (PCE) values do not necessarily serve the purposes of highway cost allocation well, since their derivation has followed from a need to determine equivalency for traffic operations purposes. Highway cost allocation demands better knowledge of equivalencies among vehicle classes, for a wide range of vehicle types, and under the full range of traffic conditions. There are several possible methods for PCE development and various suggested PCE values, but there is currently no information on the suitability of these methods and estimates for cost allocation purposes. A framework for the development of PCEs is set forth, and some final PCE values for the 20 vehicle types and 30 weight groups that could be used in the current Federal Highway Cost Allocation Study are provided. Using traffic simulation models, PCE values were calculated for each of the 12 facility types for various roadway segments (i.e., grades, length of grade, number of lanes). PCEs were also calculated for high and low traffic volumes for additional flexibility in assigning congestion-related costs. The PCEs obtained for each roadway and traffic condition were combined into a weighted-average PCE value for each vehicle type and highway facility type, reflective of the actual geometric conditions of the entire highway. Weighted-average PCEs were separately calculated for congested and uncongested conditions for two different vehicle percentages.