This page provides information about traffic in Minnesota and indicators developed by the Minnesota Environmental Public Health Tracking (MN EPHT) Program to estimate how motor vehicle traffic impacts Minnesotan communities. For more information, contact us.
Data sources
- Population data are from the American Community Survey (ACS), an annual survey conducted by the U.S. Census Bureau.
- Roadway and traffic data are from the MN Department of Transportation Traffic Forecasting & Analysis traffic volume data.
- Environmental justice area data are from the Minnesota Pollution Control Agency (MPCA).
Data questions
- The number and percent of Minnesotan residents living within 300 meters (m) of busy roads.
- How traffic exposures within environmental justice areas differ across Minnesota.
- Residential proximity indicators can be used to estimate and compare traffic exposure across communities.
- These traffic and poverty data are ecologic, meaning that they represent the average estimated exposure for the total number of residents in given area. These data are not estimates of individual residents’ poverty or income level or traffic exposures.
- Traffic indicators cannot tell us: how much or what type of air pollutants people living near busy roads may be exposed to, about local traffic composition or patterns. For example, these data cannot tell us whether local traffic in one area has more or less high-emitting heavy trucks or diesel vehicles, or whether local roads have many signaled intersections where vehicles may be idling.
Exposure indicators
The number and percent of area residents are calculated using traffic volume and population data. These methods were developed by a workgroup of the Council of State and Territorial Epidemiologists (CSTE) for Environmental Health Indicators: Air Quality.
- Traffic volume is represented as the Annualized Average Daily Traffic (AADT) on roadway segments. AADT estimates use MnDOT traffic counts and modeled values to calculate an average daily count. Because roadways contain many segments, the AADT can change between different segments of a given roadway.-Busy roads are defined as segments with AADT > 10,000.
- Buffer areas covering 300 m on either side of each busy road segment are used to estimate traffic exposure. For each census block group area – smaller than census tracts, which typically have 600 to 3,000 people – the area within the buffer is divided by the total area to calculate the percent area near busy roads.-The total block group population is multiplied by the percent area near busy roads to calculate the number of residents living near busy roads. The number of people living near busy roads is divided by the total block group population to calculate the percent of residents living near busy roads.
- Block group-level number of residents living near busy roads and total population are summed to census tract and county areas to calculate traffic exposure estimates at multiple geographic units.
Socioeconomic disparities
- Census tracts need to meet only one criteria as defined by Minnesota statute to be considered an environmental justice area. To learn more about how environmental justice areas are determined, visit the Minnesota Pollution Control Agency webpage (MPCA).
- Our method for estimating traffic exposure assumes that population is spread uniformly across block group areas. Because this method uses the percent of block group area falling within 300 m of busy roads to estimate the number and percent of people living within 300 m of busy roads, there is some error in these estimates.
To learn more about calculating traffic indicators according to CSTE guidelines, visit Council of State and Territorial Epidemiologists (CSTE) to learn more about Environmental Health Indicators: Air Quality.
To learn more about methods for traffic counting and calculating traffic volume, visit the MN Department of Transportation (MnDOT) to learn more about Traffic Forecasting & Analysis.
For more information about traffic exposure data and measures, contact the MN Data Access Portal.