The Integration of the Regional MPO Models into the Georgia Statewide Travel Demand Model – Phase 1

The integration between regional and statewide travel demand models (TDMs) can often prove difficult, or even impossible, due to discrepancies in modeling assumptions, inputs, and outputs. Discrepancies in the zonal systems, socioeconomic inputs, and transportation networks limit the ability to provide external travel estimates that can be used in regional models. Similarly, state agencies cannot easily reconcile travel demand forecasts from regional agencies with the outputs of statewide models. This research project was developed for the Georgia Department of Transportation (GDOT) and focuses on the integration of the Georgia Statewide Travel Demand Model (GSTDM) with the 14 regional TDMs used by metropolitan planning organizations (MPOs) within their respective regions and which are directly developed/managed by GDOT. To do this, the researchers propose a methodology that updates the GSTDM zonal system, socioeconomic inputs, and transportation network, and makes them consistent with the corresponding features in the MPO models. They also introduce a unified attribute table for the MPO and GSTDM networks, and a new attribute that identifies statewide-relevant links in the MPO networks, thus streamlining the process for future model updates. This project helps GDOT streamline the travel demand modeling practice, and allows the data transfer and comparison between the statewide and MPO models to take place seamlessly. The project addresses a priority for GDOT and provides guidance to other DOTs with a solution that could be transferred to and replicated in other states and agencies. It provides an efficient way to integrate MPO models into the statewide model, compare inputs and outputs across models, and simplify future model maintenance.