Assembling and Processing Freight Shipment Data: Developing a GIS-Based Origin-Destination Matrix for Southern California Freight Flows

摘要

Freight movements within large metropolitan areas are much less studied andanalyzed than personal travel. This casts doubt on the results of much conventional travel demand modeling and planning. With so much traffic overlooked, how plausible are the results. The goal of this research is to propose and execute a systematic non-survey based method to overcome this common omission and develop an origin-destination (O-D) matrix of freight flows. The authors' approach is based on secondary data sources, most of which are widely available. The authors also plan to load the estimated freight flows and concurrent passenger volumes onto the regional highway network of a large metropolitan region, the greater Los Angeles area of Southern California. The authors approach illustrates a low-cost way in which metropolitan planning agencies can meet the problem of missing freight flow information. After collecting, processing and manipulating freight data for the Southern California region from most of the available and relevant sources, the authors analyze the various freight movements in and out of the region, through the region, as well as within it. Most of the data are allocated to more than 1,500 Traffic Analysis Zones (TAZs). By integrating economic analysis, transportation modeling and GIS technologies, a GIS-based origin-destination matrix was built for Southern California freight flows. The results of the freight O-D matrix calculations are shown to be reliable through various checks with control totals. To load the freight flows onto the regional highway network, a three-step feedback transportation model was developed. It includes trip generation, trip distribution, and traffic assignment. Most of the trip generation work was done during the construction of the GIS-based origin-destination matrix.