The Florida Department of Transportation’s (FDOT) primary guide for conducting highway capacity and level of service analyses from planning through design is the Transportation Research Board’s Highway Capacity Manual (HCM). FDOT’s FREEPLAN and HIGHPLAN software programs utilize truck passenger car equivalency (PCE) values from the HCM to account for the effects of trucks on traffic flow operations. The PCE values in the HCM used for freeways and multilane highways are based on a study performed in the mid-1990s. Since that time, commercial truck performance technologies have changed. Furthermore, loading conditions are considerably different today, given the tremendous growth in freight movement. Additionally, the PCE values developed in that study were based strictly on simulation and a now outdated version of CORSIM (5.0). And finally, the PCE values taken from that study for inclusion in the HCM correspond to just a single “typical” truck (although the study considered multiple categories of trucks), which may not be representative of a typical truck in Florida, and accounting for just a single truck type may lead to considerable error in level of service results in some situations. Therefore, the objective of this project was to develop PCE values appropriate for commercial truck conditions on Florida freeways and multilane highways. The most prevalent truck types on Florida freeways and multilane highways were determined to be single unit, intermediate/interstate semi-tractor+trailer, and semitractor+double- trailer trucks. The CORSIM-NG simulation program was utilized to generate the traffic stream data for this study, as this program incorporates a more detailed truck acceleration model than other available simulation tools. In order to develop the PCE values, the methodology introduced into the literature by Sumner et al. was used. This methodology has also been utilized by others (e.g., Webster and Elefteriadou). Once the PCE calculations were run and the values were obtained for the three heavy vehicle types of interest, it was observed that PCE values generally increase with increases in proportion of grade, length of grade, traffic demand, free-flow-speed, and proportion of heavy vehicles. Conversely, the PCE values generally decrease as the number of lanes increases. Although it is difficult to directly compare the PCE values from this study to those of the HCM 2010 because the HCM values are much more generalized, for the same input conditions the PCE values from this study are generally slightly lower, which is largely due to the higher power-to-weight ratios of the trucks used in this study and the more detailed vehicle dynamics modeling. (Author/publisher)
Samenvatting