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Chattanooga-Hamilton County-North Georgia (CHCNGA) Transportation Planning Organization Travel Model Peer Review Report

4.0 Desired Model Enhancements

The CHCNGA-TPO would like to improve its travel demand model and to develop of companion land use model. They would like to use these models to measure and evaluate the impacts of several regional planning initiatives; including the use of scenario planning to contemplate alternative futures for the region and the trade-offs between them.

4.1 Land Use Model

The CHCNGA-TPO has been evaluating commercially available land use models and is considering CommunityViz and UrbanSim. These two land use model software packages can serve different purposes and cannot be directly compared. A brief summary of each land use model follows.

4.1.1 CommunityViz

CommunityViz is a GIS-based sketch planning tool useful for short-term evaluations of difference land use scenarios at a project, neighborhood, or municipal level. It is developed by Placeways, LLC in partnership with the Orton Family Foundation and functions as an ArcGIS plug-in.It uses a role-based framework that allows users to specify development constraints, land use plans, suitability and weighting factors, place types, etc.The model will then allocate development based on these parameters. It is relatively easy to use and allows for quick comparison of scenarios. Additional information regarding CommunityViz can be found at

4.1.2 UrbanSim

UrbanSim is an open source land use modeling and simulation system that can be used for medium to long term forecasting at a regional level. It was designed by Paul Waddell of the University of California, Berkeley. The UrbanSim software is implemented in Python and is packaged with a graphical user interface that collectively are referred to as the Open Platform for Urban Simulation (OPUS). OPUS provides predictions of potential outcomes of different transportation investments and land use policies. Being a simulation program, OPUS requires a great deal of data and time to be successfully implemented.Additional information regarding UrbanSim can be found at

4.2 Travel Demand Model

The CHCNGA-TPO would like to incorporate a more robust mode choice model into the overall travel model.They would like to effectively model non-motorized travel, which would be further disaggregated to walk and bicycle trips.For motorized trips they would like to be able to model transit, both local and premium services. They would like to model walk and drive access to transit with the drive access being distinguished by park-and-ride or kiss-and-ride.

The CHCNGA-TPO has interest in the "complete streets" concept where autos, transit, bicycles, and pedestrians all share the same roadway corridor. The CHCNGA-TPO would like to be able to do a better job of evaluating / modeling these types of corridors.

4.3 Model Integration

The CHCNGA-TPO would like to integrate the land use and travel demand models so that the results from one model can be readily implemented in the other. This is fairly straightforward in taking land use data and implementing it in the travel model, but becomes more complicated when taking travel model data and implementing it in the land use model.They have given consideration to some type of "accessibility index" that would measure the accessibility of an area (i.e. parcel, TAZ, etc.) by transportation mode.

Through the use of a land use model and the travel demand model the CHCNGA-TPO wants to develop sustainability and transportation performance measures that can be used to evaluate a given scenario's economic, environmental, equity benefits / impacts.

Updated: 03/28/2014
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