Environmental Justice – Traffic Proximity and Volume
This indicator reports the count of vehicles per day (average annual daily traffic) at major roads within 10 kilometers (km), divided by distance in km. Although proximity to roads can provide access to amenities, in EJScreen, the indicator is designed to screen for the negative aspects of very close proximity to very high volumes of traffic, which include asthma and cardiovascular and heart disease, among others. Areas with higher traffic proximity scores are placed higher in percentile (national ranking). The percentile could be interpreted as, for example, for a place at the 80th percentile nationwide, 20% (i.e., 100 minus the percentile) of the U.S. population lives in a block group that has a higher value.
The EJ Index for Traffic Proximity and Volume is a combination of this environmental indicator and the Demographic Index (the average of percent low-income and percent people of color).
Data are acquired from EPA’s EJScreen dataset, 2024.
Source
Source Description
EJScreen is an EPA’s environmental justice mapping and screening tool that provides EPA with a nationally consistent dataset and approach for combining environmental and demographic socioeconomic indicators. An EJ index combines demographic factors with a single environmental factor. For example, the EJ index for traffic proximity is a combination of the following populations residing in the Census block group:
- The traffic proximity indicator;
- The low-income population;
- The people of color populations.
Note that an EJ index does not combine various environmental factors into a cumulative score — each environmental indicator has its own EJ index.
The EJ index is higher in block groups with large numbers of mainly low-income and/or people of color residents with a higher environmental indicator value.
For more information, please visit the EJScreen website.
Methodology
This indicator reports the count of vehicles per day (average annual daily traffic) at major roads within 10 kilometers (or nearest one beyond 10 km), divided by distance in km from the Census block centroid. The proximity score is based on the traffic within a search radius of 500 meters (or further if none is found in that radius). This distance was selected to be large enough to capture the great majority of road segments (with traffic data) that could have a significant impact on the local residents, balanced against the need to limit the scope due to computational constraints. The closest traffic is given more weight, and the distant traffic is given less weight, through inverse distance weighting. For example, traffic 500 meters away is given only one tenth as much weight as traffic 50 meters away. Note that for this indicator, higher values (closer proximity to high volumes of traffic) are associated with higher negative health impact. Data are calculated from U.S. Department of Transportation National Transportation Atlas Database, Highway Performance Monitoring System (2019).
The percentile in EJScreen is reported as what percent of the U.S. population lives in a block group that has a lower value (or in some cases, a tied value).
The relevant EJ Index is calculated as:
where Normalized Environmental Indicator is the percentile of the particular environmental indicator source data.
For more information about this indicator or the methodology of EJScreen, please refer to the EJScreen Technical Documentation.
This indicator is available at the following subscription levels:
- Premium (currently viewing this indicator and report combination)