DEVELOPING PASSENGER CAR EQU IVALENCY FACTORS FORHEAVY VEHICLES DURING CONGESTION

摘要

The Highway Capacity Manual (HCM) utilizes Passenger Car Equivalency (PCE) factors toestimate the effect of heavy vehicles under free-flow conditions. However, these factors have been(mistakenly) used by professionals to do analyses for all traffic conditions, i.e. free-flow as well as forcedflowconditions. Recent empirical evidence suggests that the PCE factors for free-flow conditionssignificantly underestimate the effect of heavy vehicles after the onset of congestion. The current studyaims at developing PCE factors for heavy vehicles on freeways and multilane highways duringcongestion. The study utilizes empirical data and microscopic traffic simulation to develop a set of PCEfactors on level terrain and specific upgrades during congested operations. The format of the proposedPCE factors is very similar to that of the HCM PCE factors for free-flow conditions. It is believed that theuse of the proposed PCE factors for congested conditions will help to significantly improve the estimate ofheavy vehicles' effect when congestion is present.