In This Issue
Winter Bridge on Frontiers of Engineering
December 15, 2022 Volume 52 Issue 4
From novel applications of microbes to DEI in engineering to the potential for hydrogen energy, Frontiers of Engineering participants tackle today’s challenging world issues. The winter issue of The Bridge showcases research by early-career engineers as shared at the 2022 US FOE symposium.

Engineering Solutions for Justice: Transformative Approaches to Address Transportation-Related Disparities

Thursday, December 15, 2022

Author: Regan F. Patterson

When the problem statement accounts for the sociopolitical nature of the problem, opportunities emerge to reimagine and innovate systems toward equity and justice.

How a problem is defined influences its possible solutions. Transportation is recognized as the largest contributor to greenhouse gas emissions (GHG) in the United States (28 percent), and most such emissions are from passenger vehicles (EPA 2020).

Technical problems call for technical solutions. When defining the problem of transportation GHG and health-harming pollutant emissions in technical terms, the focus of analysis is typically the tailpipe and the associated problem statement is: Tailpipes emit criteria air and climate pollutants that contribute to pollution exposure and climate impacts.

But this strictly technical focus does not account for disparate exposures and impacts. For example, GHG emissions drive climate change, and the impacts and health risks of climate change disproportionately affect communities of color (Bullard and Wright 2012; Cushing et al. 2022; US GCRP 2018), as evident in Jackson, Mississippi, and Puerto Rico.

Technical and Sociopolitical Problem Framing

For transportation-related emissions, one technical solution is electric vehicles. But while electric vehicles offer an opportunity to reduce emissions exposure and climate impacts, eliminating exposure disparities requires a more expansive problem framing that goes beyond the technical orientation to comprehensively address the sociopolitical nature of the problem.

Racial-ethnic disparities in exposure to traffic-related air pollution, including nitrogen oxides (NOx) and particulate matter (PM), are well documented (e.g., Clark et al. 2017). A recent study found that low-income people of color in major US cities are exposed to 28 percent higher NO2 than high-income, non--Hispanic whites (Demetillo et al. 2021). Another found that people of color experience a 14 percent disparity in fine particulate (PM2.5) exposure compared with the US population average (Tessum et al. 2021). Disproportionate exposures contribute to racial--ethnic disparities in asthma, preterm birth, cancer, and mortality (Apelberg et al. 2005; Riddell et al. 2021; Southerland et al. 2021).

The following problem statement embraces the technical and sociopolitical dimensions of the transportation system:  The automobile-dominated transportation system disadvantages communities of color and low-income communities. Framed this way, the statement expands the focus of analysis to the entire automobile and transportation infrastructure and enables full consideration of issues to maximize equity benefits and develop a just solution in the energy transition.

Automobile-Related Issues

Nonexhaust Emissions

As the transition to electric vehicles reduces exhaust PM emissions, nonexhaust emissions—e.g., from tire, brake, and road wear and road dust resuspension—will become an increasingly important source of traffic-related PM emissions. Unlike exhaust emissions, nonexhaust emissions are largely unregulated because they are difficult to control (OECD 2020). Yet California emissions inventories show that such emissions account for 95 percent of PM10 emissions and 80 percent of PM2.5 emissions from traffic (OECD 2020).

The impact of electrification on nonexhaust emissions will be influenced by regenerative braking -systems and vehicle weight (Harrison et al. 2021; OECD 2020; Piscitello et al. 2021). Regenerative braking systems reduce brake wear, but electric vehicles weigh more than similar gasoline vehicles (Requia et al. 2018), increasing tire wear, road wear, and road dust. The problem is exacerbated by consumer preferences for larger vehicles and greater driving range (Libby 2020; OECD 2020).

Without targeted policies, some studies suggest that the increased vehicle weight of electric cars will increase nonexhaust emissions to an extent that electrification will have little effect on total traffic-related PM10 and PM2.5 emissions (Harrison et al. 2021; Timmers and Achten 2016).

Battery Production

Battery production for electric vehicles (and other uses) requires the extraction and processing of minerals and metals such as lithium, cobalt, manganese, graphite, and nickel (IEA 2021). Projections based on current and expected electrification policies estimate that demand for raw materials used in battery manufacturing will grow ninefold between 2020 and 2040 (IEA 2021).

Resource extraction contributes to environmental degradation and has human rights impacts. Lithium mining, for example, is a water- and energy-intensive process that may contaminate drinking water and deplete water resources—about 500,000 gallons of water are required to produce 1 ton of lithium (Agusdinata et al. 2018). More than half of global lithium resources are beneath the salt flats of the “lithium triangle,” an arid region of the Andes that covers parts of Chile, Bolivia, and Argentina (Agusdinata et al. 2018). In Chile’s Salar de Atacama, lithium and other mining activities have consumed 65 percent of the region’s water supply (Amui and Nkurunziza 2020).

With regard to human rights, lithium mining activities exploit Indigenous territories and fail to uphold Indigenous rights (CIEJ 2019; Marchegiani et al. 2019). Cobalt mines in the Democratic Republic of the Congo are the sites of human rights violations and child labor (Amnesty International 2016; Amui and Nkurunziza 2020).

The Biden-Harris administration plans to establish a domestic lithium battery supply chain, with domestic extraction and refining of lithium (DOE 2022; White House 2022a). The resulting impacts will affect Indigenous land rights and environmental concerns in the United States (Bosler 2021).

Auto Manufacturing

Auto manufacturing processes are sources of PM and volatile organic compound (VOC) emissions (D’arcy et al. 2016; Kim 2011). VOCs are known to cause sensory irritation, headaches, fatigue, nausea, respiratory effects, neurological toxicity, and lung cancer (Mølhave 1991; Rumchev et al. 2007).

Auto painting is the largest source of VOCs (Kim 2011). In Detroit, the Stellantis Mack Assembly Plant, a new low-emission hybrid car plant and the city’s first new auto assembly plant in 30 years, has been cited six times for air quality violations since opening in September 2021, all of them due to paint solvent and chemical odors and their health impacts on nearby residents (Grzelewski 2022; Mahoney 2022). The plant is located in a poor, majority-Black neighborhood. The US Environmental Protection Agency launched a civil rights investigation to determine whether racial discrimination influenced plant emissions permit approval (Mahoney 2022). This example demonstrates that pollu-tion from auto manufacturing sites may exacerbate environmental injustices in communities of color.

Electricity Generation

Electrification will increase electricity demand, and annual demand is predicted to be 81 percent greater in 2050 than in 2018, mostly due to electrified transportation (Zhou and Mai 2021). Electrification may shift emissions spatially from on-road exhaust systems to electric generating units (EGUs).

Health and equity benefits of electrification depend on the cleanness of the power generation mix. Fossil fuels are currently the largest sources of US electricity generation (61 percent); renewable energy sources produce 20 percent of electricity generation.[1] Studies show that electric vehicles powered by coal or the current grid mix increase air quality health impacts; renewable sources decrease such impacts (Huo et al. 2015; Tessum et al. 2014; Weis et al. 2015).

Power plants are disproportionately located in communities of color (Bullard et al. 2008; NAACP et al. 2016) and the Black population is most exposed to PM2.5 from coal electric generation (Tessum et al. 2021). One study found that Black people are the most exposed US population to emissions from all fossil fuel–fired EGUs and consequently have the largest mortality rates from those PM2.5 emissions (Thind et al. 2019).

Freeway Construction:
An Infrastructure Inequity Issue

Automobile-centric practices increase automobile dependency. From 1950 to 2016, during national freeway system construction, total vehicle miles traveled (VMT) increased 690 percent in the United States, which now also has the highest rate of vehicle ownership per capita (Frey 2018). Light-duty and truck-related VMT are projected to keep growing (FHWA 2021).

Electric vehicles powered by the current grid mix increase air quality health impacts.

In response to increased vehicle traffic, the dominant US transportation planning strategy is to expand and build new roadways. From 1993 to 2017, the country’s largest 100 urbanized areas added new freeway lane-miles at a faster rate (42 percent) than population growth in those areas (32 percent) (Bellis et al. 2020).

But transportation policies and planning too often fail to consider their community impacts. Following the Federal-Aid Highway Act of 1956, freeway construction and urban renewal inequitably affected poor communities of color, predominantly Black communities (Bullard et al. 2004; Kruse 2019; Rose and Mohl 2012). Communities of color were deliberately targeted for freeway construction, resulting in the demolition, division, and displacement of neighborhoods as well as the destruction of local economies (Bullard et al. 2004; Kruse 2019; Rose and Mohl 2012). At the same time, studies show that communities of color have lower vehicle ownership and drive less, yet are more likely to live near high traffic roads and bear a greater exposure and health burden (Kerr et al. 2021; Pratt et al. 2015; Rowangould 2013).

Infrastructure investments routinely prioritize roadways over other modes of transportation (Wilson 2020). As a result, communities of color continue to be -divided, demolished, and displaced by new construction and expansion projects. The Los Angeles Times found that over the last 30 years, federal road projects have continued to disproportionately force out Black and Latino residents (Dillon and Poston 2021).

Furthermore, studies have documented the induced demand effect, whereby added freeway capacity leads to new traffic (Bellis et al. 2020; Hymel et al. 2010). This can prompt new calls for expansion and feed the cycle of construction and congestion that devastates communities of color.

One Solution: Targeted Freeway Removal

The transition to electrification under the current transportation planning paradigm will perpetuate the harms caused by an automobile-dominated transportation system. But when the problem statement is expanded and oriented to address the socio-political nature of the problem, opportunities emerge to re-imagine and innovate the US transportation system toward equity and justice.

Efforts to reduce disparities should address root causes and repair harm (Untokening Collective 2017). One solution is to reconnect communities divided by freeways. Several highway removal projects have occurred and more are planned (Gunts 2021), largely in response to the advocacy of community-based organizations.[2]

A study that modeled the air quality and neighborhood impacts of rerouting Oakland’s Cypress Freeway and replacing it with a boulevard shows that this strategy reduces near-roadway concentrations along the original alignment (Patterson and Harley 2019). However, such removal or rerouting projects must be coupled with antidisplacement policies to ensure that intergenerational residents benefit from air quality improvements and are not excluded through environmental gentrification.[3

Black and Hispanic communities continue to be divided, demolished,
and displaced by new highway construction and expansion projects.

Federal and municipal governments are grappling with how to ensure equitable outcomes in reconnecting communities as they endeavor to repair harm from freeway division through highway removal. Federally, the bipartisan infrastructure deal invests $1 billion in the Reconnecting Communities Pilot Program, and the Inflation Reduction Act provides an additional $3 billion for Neighborhood Access and Equity Grants (US DOT 2022; White House 2022b).

At the state level, several projects—the I-375 Improvement Project in Detroit, Michigan, the I-81 Project in Syracuse, New York, and Rethinking I-94 in St. Paul, Minnesota—aim to redress racial and economic harm. The construction of I-94 led to the destruction of more than 700 homes and 300 businesses in the Rondo neighborhood in St. Paul; the loss of the 700 homes alone resulted in the loss of $157 million in intergenerational wealth (Reconnect Rondo 2020).

To support this new transportation system with fewer freeways, transportation and infrastructure investments should prioritize public transit and other sustainable modes of transport, such as walking, biking, and rolling.


Innovative, justice-focused solutions are possible when engineers ground technical work in its social and political contexts. When the guiding principle is the reduction and elimination of harm, it enables innovative solutions and creative imagination to achieve justice. In this case, that includes solutions like (re)designing communities and technologies that reduce automobile dependency and prioritize environmental justice, infrastructure equity, and transportation justice.

The question now is: What innovative, justice-focused solutions are possible when embedding the sociopolitical nature of problems becomes standard engineering praxis?


This work was supported in part by the Environmental Defense Fund.


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[1]  US Energy Information Administration, What is US electricity generation by energy source? (as of Feb 2022) ( .

[2]  See, for example, Congress for the New Urbanism, Completed Highways to Boulevards Projects ( completed-h2b-projects).

[3]  As explained in Patterson and Harley (2019, p. 2), “Urban green space, aimed at addressing environmental injustice, can make a neighborhood more desirable, potentially leading to -gentrification and the displacement of the residents for whom the green space was created.”


About the Author:Regan Patterson is an assistant professor of civil and environmental engineering, University of California, Los Angeles.