Nashville Area MPO: Regional Land Use Model
The foundation for the MPO's regional travel demand model is socioeconomic data - including population, housing, and employment estimates - organized into 2,000+ geographic subareas referred to as traffic analysis zones. Collectively, this information represents the assumed development potential for 23 municipalities and 7 counties included in the MPO's planning area.
The MPO's regional land use model, built using CommunityViz, is the tool used to predict future demographic potential of each parcel of land throughout the region. This model allocates future households and employment throughout the region based on the land use policies and each parcel of land's ability to attract new growth.
The Business-as-Usual Scenario
In 2010, the MPO published the results of a business-as-usual scenario (a.k.a. trend model) that predicted where people will live and work between now and 2035 across 10 counties in Middle Tennessee, including the seven counties that are included in the MPO's formal planning area. The model's predictions took into account adopted local land use policies and land development regulations, and each parcel's relative market suitability for attracting future growth.
How the Land Use Model Works
The basic premise of the land use model is the concept of supply and demand. The supply is simply the region's ability to accommodate new development. In other words, it's the regions "development capacity". Supply is usually determined by land use policies and/or subdivision regulations and provides specific guidelines that developers should follow when looking at a prospective piece of property. Demand is the region's predicted growth based on the region's economic outlook. This value can, (and does), change on a regular basis so it's important to monitor this and revise the demand when appropriate.
Scenario Planning to Create a Better Future
Scenario planning is a great way to provide a framework for measuring the impact of potential policy and project funding decisions on infrastructure costs, land consumption, energy costs, housing choices, and transportation choices.
Forecasting future growth using alternative growth scenarios (i.e., growth patterns), will enables the MPO to assess the implications of the anticipated growth by comparing outcomes of scenarios using a variety of solutions to fix the perceived problems of congestion, land consumption, infrastructure costs, etc.
With each scenario, certain assumptions about the business-as-usual model are changed in order to create an alternative course for future growth to occur. Changeable assumptions may include land use policy (e.g., single use, mixed-use, form-based, etc.), land development regulations (e.g., allowable densities, floor to area ratio, parking requirements, etc.), suitability factors (e.g., proximity to desirable amenities, price of land, access to infrastructure, etc.), or the anticipated amount of growth (e.g., population and employment forecasts).
Michael Skipper, AICP
Nashville Area MPO