Proposal Summary

This proposal defines a work plan for the construction of a statewide freight forecasting model for California, as the follow-up to an initial preparation phase. In that initial phase, the scope of the model was defined, the modeling methodology and data needs determined, and the software platform selected. The objective of this phase is to implement the statewide freight forecasting model so that it can be used to evaluate policy scenarios and integrate with local and state models.

The final deliverables of this project include a core model framework that can address the basic immediate needs of the state and local agencies, to be completed within a 2-year time frame. The core model is designed as a state of the art model to address the highest priority needs of the state that cannot be addressed using the state of the practice four-step commodity flow models. It consists of several primary modules: a commodity generation module, a commodity distribution module built on a destination-based logit allocation model called fractional split distribution, and a logit-based joint mode-route choice model. Factors are used to convert annual commodity flows to
daily or peak period flows, and to convert commodities to commercial vehicles which are then assigned along the routes determined from the joint mode-route choice model. The handling of transshipments in the core model will be based on either Cube Cargo’s TLN module or a network assignment approach that incorporates transfer costs that is available in TransCAD.

Several enhancement modules can subsequently be constructed and evaluated with the core model serving as a baseline. The outcome of these tests will be a set of evaluations of each enhancement in terms of the state’s needs, and a set of action plans to incorporate these enhancements to the core model by the end of 2013 to meet the needs of Senate Bill 391. Depending on the outcome of the study, potential extensions will be proposed at the end of the period expanding the data collection and modeling for the whole state.

The tasks defined for this project are split into two groups: the tasks involved in constructing and deploying the core model, and an independent set of tasks involved in evaluating the feasibility of a suite of modular enhancements. The enhancements range from minimal risk add-ons to revolutionary improvements that could redefine the landscape for statewide freight forecast models in the near future. The core model tasks include data preparation, model construction in the selected software platform, calibration, and validation of the model. A basic set of scenarios are also used to demonstrate the core model for users. The modular enhancements include: a combined commodity flow model of distribution, mode choice, and assignment along with economic supply chain interactions; a capacity-based input-output model for handling joint
distribution and mode choice with transshipment; a vehicle routing model to disaggregate and assign commodity flows onto the networks; an agent-based microscopic freight simulation model that disaggregates the freight movements into individual shipments from firm to firm; and the estimation of endogenous variables for seasonality, time of day allocation, and value of time.

A background is first presented to put the motivation and recent work in context. Following that, the proposed core model and enhancements are presented to address a list of requirements defined by the California Department of Transportation (Caltrans). A list of tasks is proposed along with an estimated timeline and budget for implementing the project.