SDRSPM Geography Definitions

The VERSPM model system supports the simulation of one or more geographic levels. This enables modules to be shared across models that operate at different scales. Geographical relationships for a model are described in the geography.csv file contained within the defs directory. This file tabulates the names of each geographic unit (except for Region) and the relationships between them. This file only allows for one-to-one relationships between Azone and Bzone; each row contains a unique relationship. When a unit of geography is not explicitly defined (i.e., it will be simulated), "NA" values are placed in the table.

The SDRSPM geography definitions follow that of the VERSPM model system:

• Region

  The region is the entire model area. Large-scale characteristics that don't vary across the region are specified at the region level. Examples include fuel prices and the carbon intensities of fuels. In the case of SDRSPM, the region is San Diego County.

• Azones

  Azones are large subdivisions of the region containing populations that are similar in size to those of counties or Census Public Use Microdata Areas (PUMAs). Azones are used to represent population and economic characteristics that vary across the region such as demographic forecasts of persons by age group and average per capita income. The Azone level of geography must represent actual geographic areas and may not be simulated. In SDRSPM, the 19 cities within San Diego County, including unincorporated areas, make up Azones.

• Bzones

  Bzones are subdivisions of Azones that are similar in size to Census Block Groups. SDRSPM uses SANDAG Traffic Analysis Zone (TAZ) as Bzones.

  Bzones are used to represent neighborhood characteristics and policies that may vary by neighborhood. For example in the RSPM:

  • District population density is a variable used in several submodels;

  • An inventory of housing units by type and district is used as a land use input; and,

  • Carsharing inputs are specified by district.

    In rural areas, Bzones can be used to distinguish small cities from unincorporated areas. Bzones may correspond to actual geographic areas or may be simulated. Bzone simulation greatly reduces model input data requirements while still enabling the modeling of land-use-related policies and the effects of land use on various aspects of travel behavior.

• Mareas

  Mareas are collections of Azones associated with an urbanized area either because a portion of the urbanized area is located in an Azone or because a substantial proportion of the workers residing in the Azone work at jobs located in the urbanized area. Metropolitan models (i.e., SDRSPM) typically only have one assigned Marea whereas state models may have several. The model system requires that each Azone may be associated with only one Marea. It is also required that all Azones be associated with a Marea. A special Marea named 'None' is used to apply to Azones that are not associated with any urbanized area. Mareas are used to specify and model urbanized area transportation characteristics such as overall transportation supply (transit, highways) and congestion. They are also used to specify large-scale land-use-related characteristics and policies in models that use Bzone synthesis. SDRSPM Mareas are defined in the following section.

SDRSPM Geography Definition Summary

• Azone: 19 cities in San Diego County

• Bzone: SANDAG TAZ (version 13)

• Czone: Not Applicable

• Marea:

  • Definition: the union of core urban area and area with 2016 transit service. The resulting number of TAZs is 3064.
  • Marea-specific MGRA is stored at: SQL2014b8\RM.DBO.AreaType_MGRA
  • Urban area is one of the location types in Marea-specific MGRA.

Area_Type	SANDAG definition	Loc_Type
Central Business District	The financial and Gaslamp districts found within Centre City San Diego	Urban
Major University	CSUSM, SDSU, UCSD, and USD	Urban
Urban	Large and diverse areas with moderate density. Single and multi-family ;dwelling ;units (DUs) ;and diverse non-residential uses. The urban core of San Diego	Urban
Second City	Large and diverse areas with moderate and high density. Primarily multi-family DUs, and typically includes diverse employment opportunities	Urban
Town Center	Small urban job centers, possibly with moderate residential densities, typically includes higher employment densities	Urban
Suburban	Low density, primarily single-family DUs with lot sizes less than ½ acre. Includes other uses such as neighborhood serving strip malls and offices	Town
National / State / Regional Park	Developed and undeveloped park and open space land	Rural
Rural	Very low density, primarily single-family DUs with large lot sizes. Includes agricultural and some other very low-density non-residential uses	Rural
Tribal	Land administered by Sovereign Tribal Nations, some of which include casinos	Rural
Village	Small Towns associated with County CPAs. Small in size ;with low-to-moderate density and diversity. Typically surrounded by Rural area types	Rural
Military	Land administered by branches of the United States Military	Rural
Port of Entry	Land administered by the United States Customs and Border Patrol	Rural
Tourist Attraction	The Zoo, Sea World, Lego Land, etc.	Rural
Bay	San Diego Bay proper includes clusters of population living on moored boats, and some maritime employment including the salt ponds in south bay(e.g.,San Diego Bay and Mission Bay)	Rural

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