Traffic volume*

Average traffic volume per meter of major roadways in the county.

The 2021 County Health Rankings used data from 2019 for this measure.

Reason for Including

Residential proximity to motor vehicle traffic is associated with increased exposures to ambient noise, toxic gases and particulate matter, including diesel particulates. Based on the available evidence, residential proximity at a distance of roughly 100–300 meters is related to poorer health outcomes.[1,2] This proximity to traffic has been associated with various health impacts for residents, particularly asthma exacerbation and possibly onset of asthma, as well as increased mortality rates.[3,4] Living in proximity to traffic has also been associated with subclinical atherosclerosis (a key pathology underlying cardiovascular disease (CVD)), prevalence of CVD and coronary heart disease (CHD), incidence of myocardial infarction, and CVD mortality.[5] Proximity to traffic can also mean increased noise exposure, which is linked to stress and poorer health outcomes.[6]

Key Measure Methods

Traffic Volume is an Average Rate 

The county-level measure is calculated by aggregating all the census block data within a county, and weighting by the number of people in the corresponding blocks. The measure is reported as the average count of vehicles per meter per day within 500 meters of a census block centroid (the center point of a census block), divided by distance in meters, presented as the population-weighted average of blocks in each county.

Calculation Explanation

The proximity score for traffic looks within a search radius of 500 meters (or further if none is found in that radius). The closest traffic is given more weight through inverse distance weighting. A highway with 16,000 AADT (Annual Average Daily Traffic) at 400 meters distance would result in a score of 16,000/400=40.  More information: https://www.epa.gov/sites/production/files/2015-05/documents/ejscreen_technical_document_20150505.pdf#page=13.

Roadways Included

All interstate, principal arterial, other National Highway System and HPMS sample sections.

Measure Limitations

This measure does not capture exposures that occur away from the block centroid (assumption that homes are equally distributed from the center of the census block).

While increased traffic volume in a county may be associated with harmful exposures, it may also be related to factors that positively influence health, such as commerce and employment opportunities. Residential proximity to roads can provide access to jobs, health care, food, recreational opportunities, and other benefits.

There is a relatively large data-year lag (~5yrs). One-third of the data is updated annually. Entirely new data is released every three years.

States collect and report these data differently. Traffic counts are performed by state Departments of Transportation, so this measure is not comparable across states.

Can This Measure Be Used to Track Progress

This measure is not appropriate for measuring progress. 

Data Source

Years of Data Used

2019

EJSCREEN: Environmental Justice Screening and Mapping Tool

EJSCREEN is an environmental justice mapping and screening tool that provides EPA with a nationally consistent dataset and approach for combining environmental and demographic indicators. EJSCREEN users choose a geographic area; the tool then provides demographic and environmental information for that area. All of the EJSCREEN indicators are publicly-available data. EJSCREEN simply provides a way to display this information and includes a method for combining environmental and demographic indicators into EJ indexes. 

EJSCREEN includes:

Digging Deeper
Age 0
Gender 0
Race 0
Education 0
Income 0
Subcounty Area 1

This measure can be analyzed at smaller geographies. EJScreen provides Census Blockgroup estimates. 

References

[1] Beelen R, Hoek G, van den Brandt PA, et al. Long-term effects of traffic-related air pollution on mortality in a Dutch cohort (NLCS-AIR study). Environ Health Perspect. 2008;116(2):196–202. doi:10.1289/ehp.10767

[2] Hulsey B, Hopkins E, Olson E, Burg E, and Carlson M. Highway Health Hazards: How highways and roads cause health problems in our communities—and what you can do about it, Sierra Club, 2004, 6 Draft Environmental Impact Report/ Environmental Consequences, and Environmental Impact Statement Avoidance, Minimization, And/Or Mitigation Measures, I-405 Improvement Project, May 2012.

[3] Baumann, Lauren M. et al. Effects of distance from a heavily transited avenue on asthma and atopy in a periurban shantytown in Lima, Peru. Journal of Allergy and Clinical Immunology, Vol 127, Iss 4, 875 – 882.

[4] Brunekreef B, Beelen R, Hoek G, Schouten L, Bausch-Goldbohm S, Fischer P, Armstrong B, Hughes E, Jerrett M, van den Brandt P. Effects of Long-Term Exposure to Traffic-Related Air Pollution on Respiratory and Cardiovascular Mortality in the Netherlands: The NLCS-AIR Study. Health Effects Research Report 139, 2009. https://www.healtheffects.org/publication/effects-long-term-exposure-traffic-related-air-pollution-respiratory-and-cardiovascular

[5] Hoffman B, Moebus S, Dragano N, Mohlenkamp S, Memmesheimer M, Erbel R, Jockel KH, Heinz Nixdorf Recall Investigative Group. Residential traffic exposure and coronary heart disease: results from the Heinz Nixdorf Recall Study. Biomarkers. 2009 Jul;14 Suppl 1:74-8. doi: 10.1080/13547500902965096.

[6] Sørensen M, Andersen ZJ, Nordsborg RB, Jensen SS, Lillelund KG, Beelen R, et al. Road Traffic Noise and Incident Myocardial Infarction: A Prospective Cohort Study. PLoS ONE, 2012, 7(6): e39283. https://doi.org/10.1371/journal.pone.0039283

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