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Enhancement of Transportation Network Analysis Tools for Truck-related Planning and Operations

Proposal Summary and Objectives

The state-of-the-art in traffic operations analysis methods that explicitly consider the impacts of large trucks has improved considerably over the last decade. Micro-simulation tools and deterministic analytic methods such as those in the Highway Capacity Manual (HCM) offer reasonably robust methods for explicitly accounting for large trucks. However, there are still several areas where improvements in the methods and the tools are needed. Two areas, in particular, are network-level analysis and travel time reliability analysis, and even more so, the combination of these two areas. Conducting the network-level analysis entails the modeling of traffic assignment that can accurately forecast the truck flow distribution.

However, most of the existing models do not work well due to their restrictive assumption that the passenger car equivalent (PCE) value of trucks is flow-independent, i.e., the PCE value is given and does not vary with traffic conditions. Such an assumption is not consistent with the HCM, although it can simplify the model. On the other hand, while micro-simulation is very suitable for performing network-level analysis, the computational burden can become unreasonable when travel time reliability analysis is factored in, as this will increase the number of simulation runs several-hundred fold. The HCM includes methods for analyzing travel time reliability, but only at the facility level.

This project aims to improve the state-of-the-art for accounting for the impact of trucks at the network level. This will be accomplished in two ways: 1) extending the methodology for multiclass user- equilibrium (UE) traffic assignment to account for flow-dependent PCEs of trucks, and 2) using the HCM freeway facility analysis methodology to calculate travel time in the UE route choice methodology instead of the traditional BPR (Bureau of Public Roads) function.

Funding Amount: $175,000
Status: Complete
Duration: Aug. 1, 2017 - Sept. 30, 2018

Final Report