The Traffic Analysis Zone (TAZ) layer is a geographic unit that represents a small area within the Metrolina region. It stores information related to the socioeconomic database and serves as the origin and destination for all tours. Each TAZ has a TAZ ID number that can be joined with the socioeconomic database.

TAZ Database

The TAZ structure consists of 3,896 zones and spans 13 counties. Each TAZ is connected to the highway networks by centroid connectors. The TAZs were updated to align with the new 2020 US Census geographies and the addition of Anson County to the model region. This process involved the reshaping and splitting of the previous TAZ structure, adding and relocating centroids and centroid connectors, and a review/ revision process with regional partners.

External zones are defined using a polygon-based method. This means external stations are drawn as cordon TAZs just outside the study area, where traffic enters and exits.

The map below shows the changes made in the TAZ structure moving from 3,578 TAZs in MRM22v1.0 to 3,896 TAZs in MRM25v1.0

Socioeconomic Database

The Socioeconomic (SE) or land use data is a primary an input into the travel demand model. The SE data consists of estimates of population, households, student enrollment and employment. In 2023, a study was conducted by an independent demographer to provide updated regional and sub-regional (county and district) population, household, student enrollment, and employment projections for the region. This study was completed under the direction of the MRM’s regional partners.

The household data consists of:

  • Households
  • Total Population
  • Household Population
  • Median Household Income
  • Group Quarter Population

The employment data consists of eight primary categories of employment and correspond to the the North American Industry Classification System (NAICS). To view the the MRM NAICS groupings click here.

  • Low-Traffic Industrial Jobs
  • High-Traffic Industrial
  • Retail
  • High-Traffic Retail
  • Low-Traffic Service
  • High-Traffic Service
  • Education
  • Office

To view the socioeconomic database structure within the MRM click here.

Area Type

Area type is one of the inputs to the speed and capacity calculations of the network. Area type is calculated based on residential and employment density within a 1.5-mile radius of the TAZ center.

Each TAZ is assigned one of five area types:

  • Central Business District (CBD)
  • Central Business District Fringe/Other Business District (OBD)
  • Urban
  • Suburban
  • Rural

The table below shows the criteria used for each area type.

Employment Density (Employment/Square mile)
Population Density (Population/Square mile) 0-2,600 >2,600 >10,500
Less than 375 Rural (5) CBD Fringe/OBD (2) CBD (1)
Greater than or equal to 375

Urban (3) - If POPDEN + EMPDEN/1.6 is greater than 2,100

Suburban (4) - If POPDEN + EMPDEN/1.6 is less than or equal to 2,100

POPDEN is the population per square mile, and EMPDEN is the employment density per square mile. The area is the TAZ area after excluding water and protected open space.