published journal article
published journal article
This paper examines how local knowledge about migration destinations affects housing tenure decisions for movers in the US, particularly long-distance movers–those who have moved more than 50 miles–while considering other channels of information. Using data from the American Community Survey from 2012 to 2019, we find that among long-distance movers, geographic distance seems to lower the likelihood of owning their next home, while social connectedness can mitigate this effect considerably. This result is robust across different empirical specifications. Our analysis also shows that these channels of information may have significantly different implications for short-distance movers’ housing tenure choices compared to long-distance movers.
published journal article
In low-demand areas or during off-peak hours, fixed-route bus services often show low productivity when maintaining regular headways. Reducing headways further decreases service quality, presenting a challenge for transit agencies. This paper proposes a novel approach to solve the low productivity issue, by forming a partnership between transit agencies and Transportation Network Companies (TNCs), where TNC vehicles substitute fixed-route buses in certain segments. The study introduces a decision-making framework to help transit agencies assess when and where such partnerships are operationally feasible and financially sustainable. It identifies key factors that influence the viability of TNC substitution, including vehicle hours, mileage, and passenger loads. Based on these factors, the paper explores various compensation schemes and determines the cost of TNC operations—a critical component of the framework. The proposed framework is evaluated using a real-world case study in Long Beach, California, USA. Findings suggest that in low-demand scenarios, specifically when the number of passengers per stop is fewer than 0.5, replacing buses with TNC services reduces operating costs. The results also indicate that transit agencies should consider both cost savings and passenger experience while making substitution decisions, as truncating longer route segments may yield lower savings but may improve service for additional passengers. Overall, this research provides valuable insights for transit practitioners seeking to reduce expenses and enhance service quality in low-demand areas and off-peak hours through innovative public–private partnerships with TNCs.
published journal article
published journal article
We surveyed and interviewed oil refinery workers who lost their jobs when a refinery in California shutdown in October 2020 to document post-layoff employment outcomes. Workers experienced post-layoff median hourly wage losses of 24 percent, a 26 percent unemployment rate, and reported frustrating job search experiences marked by a difficulty to convey skills to new employers. Our study harbingers future transition experiences of fossil workers and identifies social insurance responses that could inhere within climate change policies to shield workers from economic risk. Workers identified a need for third-party certification of their skills, benefits negotiators, and wage supports.
published journal article
published journal article
The complex urban life has prompted commuters to combine non-work activities with their work trips to save time and money, resulting in commute-based trip chains closely tied to mode choice. Dhaka, one of the world’s most densely populated megacities and the capital of Bangladesh, exhibits the potential for unique trip chaining patterns driven by its complex land use and extensive range of transport options. This study examines the trip chaining behavior of commuters in Dhaka, utilizing Latent Class Analysis (LCA) to categorize them based on their trip chaining and mode use characteristics. The analysis reveals four distinct commuter classes. Class 1 represents simple trip chain makers, traveling without additional stops between home and work, using motorized transport. They typically belong to middle- to high-income households with access to private vehicles. Class 2 is characterized by complex trip chain makers – individuals who combine work and non-work activities – primarily during the journey to home, utilizing motorized vehicles. Females and those from middle- to high-income households tend to fall into this group. Class 3 consists of simple trip chain makers who rely on public transit or non-motorized vehicles. These commuters are mainly low-income males without access to private vehicles. Finally, Class 4 represents complex trip chain makers using non-motorized transport and typically belong to middle-income households with no private vehicle access. The findings offer valuable insights into the complex travel behavior of commuters, aiding the development of effective travel demand management policies, particularly in addressing peak-hour traffic contributed by commuters.
MS Thesis
Most existing traffic flow models rely on data collection methods that require a detailed layout of networks with compilations of recorded individual trip data. Although these procedures have been reliable, they also possess disadvantages such as high computation costs and a lack of privacy protection. Thus, in search of a lower cost alternative that can also effectively protect consumer privacy, we analyzed the Bathtub traffic flow model as a potentially viable data collection protocol.To test whether concepts can be proven, conservation equations can be consistent, and outputs can be obtained with accuracy through the Bathtub model, I performed model calibration and validation on data provided by Bluebikes, Metro Boston’s public bike share program. The following components were tested: unified relative space paradigm, conservation equations, and Bathtub model. These components were tested through the following steps: data organization, definition of steps, Bathtub model selection, Bathtub variables, Bathtub relative variables, average speed, conservation equation validation, and model solution. The unified relative space paradigm unified the network trips using remaining trip distances. Bluebikes trip distance distribution showed a log-normal distribution, which failed to meet the negative exponential and time-independent trip distance distribution assumption. The conservation in total trips equation was validated with perfect accuracy, while the conservation in trip-miles-traveled equation was validated with good accuracy. The generalized Bathtub model solution also produced accurate results, where space-mean speed yielded the best results. Given the model’s novelty and potential for privacy-preservation and application, there are many possibilities for future study, such as: data collection protocols with the Bathtub model, compatibility with other transportation modes, and comparisons with reality. This study establishes the preliminary step in putting theory to practice, as we aim towards application.
MS Thesis
Vehicle dismantling facilities play a critical role in recycling metals from end-of-life vehicles (ELVs). However, these facilities can impose environmental burdens on nearby communities, including noise, air pollution, and groundwater contamination, especially when operations do not comply with legal standards. While the siting of hazardous facilities has been widely studied through an environmental justice (EJ) lens, vehicle dismantlers have received limited attention. This study examines these patterns in California, highlighting their unique characteristics and implications for social and environmental equity. Using a Heteroskedastic Binary Logit model to capture local differences, this thesis shows that vehicle dismantlers are more likely to be located in census tracts with higher levels of social disadvantage, although not disproportionately in low-income areas. Composite variables, such as the CalEnviroScreen score and components of the Social Vulnerability Index, are important for predicting the presence of dismantlers, linking these facilities to broader patterns of environmental and social vulnerability. While results do not explicitly find racial disparities, findings suggest that vehicle dismantlers are concentrated in highly polluted areas, which are often disproportionately inhabited by disadvantaged populations, which raises environmental injustice concerns. Conversely, population density is also a significant factor, which is inversely correlated with the presence of vehicle dismantlers. These facilities often require substantial land, which is expensive in densely populated urban areas. A better understanding of the factors influencing the siting of these facilities is useful to craft better policies to address social and environmental injustices, promote sustainability and enhance social equity.
conference paper