摘要: |
The Texas Department of Transportation (TxDOT) developed the Texas Statewide Analysis Model (SAM) to provide analysis and forecasting capabilities of passenger and commodity/freight movements in Texas. The SAM provides data and results at a level that is more aggregate than that typically accomplished within urban areas in their travel demand models. Travel demand models for urban areas typically concentrate on person estimates and at an aggregate level also estimate commercial vehicle (i.e., truck) movements. To produce consistent compatible estimates of passenger and commodity/freight movements, agencies have not integrated the SAM and urban travel demand models. The purpose of this research was to provide a Texas analysis model that would disaggregate statewide estimates of commodities/freight within the Texas traditional urban travel demand model boundaries. The research has developed a disaggregation model for integrating the SAM commodity estimates into the urban framework and a bottom-up model for estimating the commodity movements internal to the urban area that occur in addition to statewide movements. The integration of the SAM estimates involves disaggregation of internal to internal, external to internal, and external to external movements. The SAM accomplishes disaggregation using existing demographic data at the urban level. The urban model component uses data from typical urban travel demand models, including software currently used by TxDOT in their urban travel demand models. Modeling data such as shipping/receiving rates, trip length, load factors, etc. were developed from travel surveys done as part of the state travel survey program. The urban model also specifically estimates vehicle (truck) movements that do not involve the transfer of commodities as well as movements of empty vehicles. Included in the research was the application of the urban model and integration of the SAM estimates for the Houston-Galveston Area to develop estimates of commodity movements in the Houston-Galveston Area and estimate the truck movements associated with those commodities. |