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Traffic Impacts

Variable Definitions:
Traffic Impacts Percentile: The percentile of a given area’s exposure to particulate emissions due to vehicle exhaust, based on traffic volume and road lengths, compared to the rest of LA County

Methodology Note:
The original CalEnviroScreen dataset provides percentiles across all California census tract. However, these percentiles are recalculated exclusively within Los Angeles County census tracts to fit NDSC’s geography.

For more information on the California Office of Environmental Health Hazard Assessment’s methodology, visit the CalEnviroScreen homepage.

California Office of Environmental Health Hazard Assessment – CalEnviroScreen 2.0 (2014), CalEnviroScreen 3.0 (2017), CalEnviroScreen 4.0 (2021)

Years Available:

CalEnviroScreen 2.0: 

Data collected from 2009-2011 and published in 2014

CalEnviroScreen 3.0: 

Data collected from 2012-2014 and published in 2017

CalEnviroScreen 4.0: 

Data collected from 2017-2019 and published in 2021

Why are these variables important to measure?

Traffic impacts represent the vehicles in a specified area, resulting in human exposures to chemicals that are released into the air by vehicle exhaust, as well as other effects related to large concentrations of motor vehicles

While California has the strictest auto-emission standards in the US, the state is also known for its freeways and heavy traffic. Traffic is a significant source of air pollution, particularly in urban areas, where more than 50% of particulate emissions come from traffic. Exhaust from vehicles contains a large number of toxic chemicals, including nitrogen oxides, carbon monoxide, and benzene. Traffic exhaust also plays a role in the formation of photochemical smog. Health effects of concern from these pollutants include heart and lung disease, cancer, and increased mortality. 


 August, Laura, et al. “CalEnviroScreen 4.0.” Oehha.ca.gov, Oct. 2021, https://oehha.ca.gov/calenviroscreen/report/calenviroscreen-40.

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