On Wednesday, March 30^th, the Pacific Southwest University Transportation Center (PSR) hosted Professor Geoff Boeing and USC Urban Planning and Development PhD students Yougeng Lu and Clemens Pilgram for a seminar on the environmental justice issues of vehicle pollution. Titled “Local Inequities in the Relative Production of and Exposure to Vehicular Air Pollution in Los Angeles,” the seminar featured METRANS-funded research from Dr. Boeing and his team. Dr. Boeing is an Assistant Professor at USC’s Sol Price School of Public Policy and the Director of USC’s Urban Data lab. Dr. Boeing’s research revolves around city planning, urban form, data science, and urban informatics.

Dr. Geoff Boeing

The seminar was the first research seminar hosted by PSR for the spring semester and drew an enthusiastic audience of transportation researchers, practitioners, and students. The session began with a formal presentation and ended with a discussion of the audience’s questions.

Dr. Boeing began the presentation by narrating the history of the freeway system in Los Angeles County. Beginning in the late 1930s, plans emerged for a regional freeway system. By the 1960s, freeways had entered the cultural consciousness of Los Angeles and the freeways served as tourist attractions similar to amusements parks. For all of the accessibility created by freeways, every freeway built through developed parts of Los Angeles had to erase a community that was in its path. Neighborhoods that were cleared to build the freeways were often minority, lower income neighborhoods that held less political power than affluent, white neighborhoods. Additionally, freeways brought the onset of automobile-created air pollution to neighborhoods adjacent to the freeways.

The two research questions Dr. Boeing and his team aim to answer with their research are: 1) Are different communities exposed to vehicular pollution at a level proportional to how much they drive? 2) If not, what is the relationship between race/class and this disparity in production of and exposure to vehicular pollution?

The research used several data sources including traffic related particulate matter (PM) 2.5 concentrations from privately owned local air sensors, demographic data from the 2014-2018 American Community Survey, journey to work data from Longitudinal Employer-Household Dynamics Origin-destination Employment Statistics (LODES), and freight volume data from the Southern California Association of Governments. The geography unit used was the census tract. The research developed an indicator called burden ratio (BR) to measure the ratio of exposure (to vehicular air pollution) to production (driving). Census tracts with higher exposure to air pollution but less driving would have a higher burden ratio.

To study demographic disparities, the research looks at origin-destination (O-D) pairs between residences and workplaces. In general, the goal was to identify commuters from white and non-white census tracts and determine how the commuting routes differ. Simulation modeling was used to estimate commute routes. The commute simulation found that white commuters traverse non-white tracts to travel to their workplaces while non-white commuters traverse less-white tracts on their way to their workplaces.

The research team went further and developed an inequity index to evaluate disparities in driving patterns between white commuters and non-white commuters. Positive inequity index values mean a disproportionately high distance was traveled by white commuters through a tract and negative inequity index values mean a disproportionately low distance traveled by white commuters through a tract.

Results from a regression analysis found a negative relationship, meaning that all else held constant, people who drive more are less exposed to pollution and traffic. Areas with a greater share of white population are less exposed to vehicular pollution. In a majority of census tracts, people who drive more are less exposed to vehicular pollution. Results from the inequity index show that more white people drive through non-white areas than vice versa, thus exposing non-white communities to higher levels of air pollution generated from vehicles despite these communities driving less.

Dr. Boeing then wrapped up by reflecting on what can be done. Although there are no easy answers for this immense issue, Dr. Boeing suggested fuel efficiency and vehicle electrification, capturing externalities through a congestion/emissions tax, discouraging high-income commutes with work from home policies, and reassessing housing policies and zoning that helped motivate the original placement of highway infrastructure.   

About the Author:

Hayley Rundle is a second-year Master of Urban Planning student at the USC Price School of Public Policy, concentrating in Mobility and Transportation Planning. Hayley is interested in sustainable transportation planning to improve environmental quality, equity, and mobility for all. Hayley serves as the team leader for the METRANS Industry Engagement and contributes to the Student Research Team, summarizing cutting edge transportation research projects and findings for the METRANS Fast Facts for Students series.