conference paper
conference paper
The Alameda corridor provides a crucial rail link for moving freight in and out of the Ports of Los Angeles and Long Beach, also known as the San Pedro Bay Ports (SPBP). While the benefits of this trade are enjoyed by the whole nation, the associated air pollution costs are born mostly by the people who live in the vicinity of the Alameda corridor and the two freeways (the I-710 and the I-110) that serve the Ports. Although they are more energy efficient than trucks, trains contribute heavily to regional air pollution; in addition, rail traffic in the South Coast Air Basin is projected to almost double in the next twenty years. This paper presents an analysis of the emissions and the dispersion of PM and NOx emitted by train operations in and around the Alameda corridor. We find spatial and temporal variations in the dispersion of these pollutants, which justifies our approach. Moreover, the railyards in our study area are responsible for the bulk of PM and NOx emissions (compared to line haul operations). While PM emissions from train operations contribute only a fraction of the recommended maximum concentration, NOx emissions go over recommended guidelines in different areas. The affected population is mostly Latino or African American. Our approach is also useful for better understanding trade-offs between truck and rail freight transport.
conference paper
published journal article
Human mobility is considered as one of the prominent non-pharmaceutical interventions to control the spread of the pandemic (positive effect from mobility to infection). Conversely, the spread of the pandemic triggered massive changes to people’s daily schedules by limiting their movement (negative effect from infection to mobility). The purpose of this study is to investigate this bi-directional relationship between human mobility and COVID-19 spread across U.S. counties during the early phase of the pandemic when infection rates were stabilizing and activity-travel behavior reflected a fairly steady return to normal following the drastic changes observed during the pandemic’s initial shock. In particular, we applied Structural Regression (SR) model to investigate a bi-directional relationship between COVID-19 infection rate and the degree of human mobility in a county in association with socio-demographic and location characteristics of that county, and state-wide COVID-19 policies. Combining U.S. county-level cross-sectional data from multiple sources, our model results suggested that during the study period, human mobility and infection rate in a county both influenced each other, but in an opposite direction. Metropolitan counties experienced higher infection and lower mobility than non-metropolitan counties in the early stage of the pandemic. Counties with highly infected neighboring counties and more external trips had a higher infection rate. During the study period, community mitigation strategies, such as stay at home order, emergency declaration, and non-essential business closure significantly reduced mobility whereas public mask mandate significantly reduced infection rates. The findings of this study will provide important insights to policy makers in understanding the two-way relationship between human mobility and COVID-19 spread and to derive mobility-driven policy actions accordingly.
conference paper
published journal article
conference paper
working paper
As public funds become ever more scarce and demands on them ever greater, public scrutiny of their use increases. Means are sought to determine exactly how such funds are being used, and to determine where and how they could be better allocated. The quantitative evaluation of performance provides some measure of rational justification for political and policy decisions. Public transit is today in this position of stabilized or decreasing funds and increasing demands, yet there exist no readily applicable means of evaluating transit performance. Transit must adapt the evaluation techniques and learn from the experience of other public fields. Performance evaluation has long been an issue in the fields of public education, housing, and health. Many volumes of research are available discussing evaluation theory and experience with techniques ranging from performance contracts and peer ratings to subjective ratings of “satisfaction”. Performance evaluations are also conducted in many other public service fields, e.g. fire and police services. Yet, the fields of education, housing, and health are similar to public transit in that they: (1) must be provided on a continuous basis; (2) cannot be nor mally justified on a public safety basis, as can police and fire ser vices; and (3) are not utilized by the entire population on a regular basis. This paper will investigate each of the fields (public education, housing, and health) in turn, discussing the predominant evaluation techniques used or suggested for that field and the problems inhibit ing’ evaluation. For each area, appropriate parallels will be drawn to the evaluation of public transit.
conference paper
published journal article
Background: Investigating human exposure to toxic contaminants through dietary consumption is critical to identify disease risk factors and health guidelines. Methods: In this study, we developed a cross-sectional online survey to collect information about dietary patterns and related food consumption habits among adults (age ≥ 18) and adolescents (ages 13–17) in Southern California, focusing on popular staple foods and/or those targeted most commonly under California’s Proposition 65 law for lead and acrylamide exposure. Results: Results identified root vegetables, rice, leafy greens, pasta/noodles, tea, juice, and seafood to be among the most heavily consumed foods by mass, while the daily intake of many foods such as stuffed grape leaves, tamarind/chili candy and herbs/spices varied by age and race/ethnicity, suggesting that many of Proposition 65’s pollution allowances may be exacerbating issues of health inequity and environmental injustice. Moreover, findings from this study indicate that the methods of exposure assessment often applied under Prop 65, especially relating to herbs/spices, are likely to underestimate single-day exposures, thus allowing unsafe products on the market without warning labels. Conclusions: Study outcomes are broadly relevant to environmental health and nutrition science, with particular relevance to public health practitioners and California’s Prop 65 regulators and other stakeholders.