UC Berkeley

In goods movement corridors, some freeways and local arterial roadways are heavily trafficked by heavy-duty diesel trucks. Heavy-duty diesel trucks are major sources of air pollution. Localized impacts of diesel exhaust have environmental justice implications for communities near port and goods movement truck activity. These communities are disproportionately burdened by exposures and associated health risks. Predominately nonwhite and low-income communities are concentrated in goods movement corridors due to sociospatial processes, such as residential segregation. Policies that mitigate heavy-duty diesel truck exposures have the potential to address disproportionate exposure burdens. Two recently implemented policies that reduce exposures are the use of diesel truck emission controls and truck rerouting. In this dissertation, I examine the impact of these policies on near-roadway concentrations of diesel-related air pollution. This dissertation provides new policy-relevant insights by quantifying the environmental justice and equity outcomes of air pollution mitigation strategies for heavy-duty diesel trucks. This analysis is significant because it illustrates a systematic approach for incorporating quantitative measures of inequality and injustice within analyses of diesel truck-related policies. This formal process can be used to inform the future design and implementation of policies and initiatives, particularly in highly impacted areas.

The pollutant dispersion model RLINE was used to predict near-roadway concentrations of nitrogen oxides (NOx) and black carbon (BC). Model predictions were compared with continuous, yearlong records of measurements from two near-roadway sites in the San Francisco Bay Area. Heavy-duty diesel trucks were a significant source of NOx and BC at both sites. Characterization of temporal variations in heavy-duty truck activity on diurnal, weekly, and seasonal scales was included in this analysis; truck traffic and emissions are not well-correlated with passenger vehicle or total traffic volumes. For both pollutants, more than 90% of predicted 24-hour average concentrations were within a factor of two of observations at both near-roadway monitoring sites. The model responds appropriately to seasonal variations in meteorology and day-of-week variations in emissions. Model performance for NOx was better overall than for BC. Reducing uncertainties in emission factors would help to improve model performance for BC.

The air quality and environmental equity benefits that result from accelerated use of diesel particle filter (DPF) and selective catalytic reduction (SCR) systems on heavy-duty diesel trucks are assessed in this dissertation. My research focuses on communities in Oakland, California, adjacent to two major freeways: Brookfield Village and Sobrante Park along I-880, which are heavily affected by truck traffic; and Sequoyah along I-580 where heavy-duty trucks are prohibited. Brookfield-Sobrante has a higher proportion of nonwhite, low-income residents than Sequoyah (97% versus 76%). I modeled concentrations of nitrogen oxides (NOx), diesel particulate matter (PM), and black carbon (BC) prior to widespread use of diesel emission controls (2009), after universal adoption of DPFs to control PM emissions (2018), and after universal adoption of SCR to control NOx emissions (2023). Reductions in mean near-roadway pollutant concentrations in Brookfield-Sobrante were 63±3% for NOx and 48-49±4% for diesel PM and BC by 2018. In Sequoyah, reductions in mean NOx concentrations were smaller (52±3%), and mean diesel PM and BC concentrations increased by 19±7% and 15±6%, respectively. While estimated NOx concentrations remain higher in Brookfield-Sobrante compared to Sequoyah, diesel PM and BC concentrations will be similar in both neighborhoods by 2023. Reductions in diesel emissions also led to improvements in equity when quantified by the difference in mean intakes for Brookfield-Sobrante versus Sequoyah. Exposure inequities decreased more for diesel PM and BC than NOx. Maintaining these air quality and equity benefits requires that diesel emission control systems remain in good working order over time.

The effects of freeway routing decisions on exposure to diesel-related air pollution and neighborhood socioeconomic and demographic change are also investigated. Freeway rerouting and replacement with a street-level boulevard are urban transportation policies that may help redress disproportionate air pollution burdens resulting from freeway construction that took place during the mid-20th century. However, environmental justice activism for freeway rerouting may have the unintended consequence of environmental gentrification. I focus on the effects of rerouting the Cypress Freeway in West Oakland along with construction of a street-level boulevard (Mandela Parkway) on the original freeway alignment. The impacts of two rebuild scenarios, freeway rebuild-in-place and reroute, on near-roadway NOx and BC concentrations are compared. I also assess changes in demographics and land use in West Oakland between the time when the Cypress Freeway was damaged by a major earthquake and after completion of Mandela Parkway. My research indicates that freeway rerouting reduced annual average concentrations of both NOx (–38±4%) and BC (–25±2%) along the Mandela Parkway alignment. However, there is evidence of environmentally-driven neighborhood change, given that there are larger decreases in the long-time Black population (–37%) and increases in property values (229%) along the residential portion of the Mandela Parkway corridor compared to West Oakland as a whole. There are some attributes along the Mandela Parkway that enable low-income residents to live in proximity to the street-level boulevard, such as affordable housing.

Recommendations for future research include developing longitudinal community-based participatory traffic count surveys, evaluating model predictions of air pollution using new local-level monitoring techniques, and assessing relationships between diesel policy-related changes in air pollution and associated health outcomes.