Phd Dissertation

Case Studies in Secure Contracting and Communication in Transportation Systems

Abstract

Advancements in Information and Communication Technologies have led to the proliferation of Intelligent Transportation Systems (ITS). These systems leverage emerging technologies to address the challenges of traditional transportation systems. As the number of connected devices continues to increase, smart cities and communities are reliant on ITS as apart of their ecosystems. ITS are efficient and sustainable mobility systems that leverage emerging technologies to securely interact with other transportation systems and entities. This dis- sertation explores three case studies in privacy preserving contracting and communication among vehicles in transportation systems. The first case involves paratransit systems where we explore paratransit agency adoption of complementary ride-hailing services through se- cure contracting. The second case involves Vehicular Ad-hoc Networks in which we analyze the communication and data exchange between vehicles in the network. In the last case, we introduce smart infrastructure in the analysis of ITS and traffic in smart city environments by modeling the shift in traffic behaviors through the use of dynamic traffic lights. The major contributions of this dissertation are in the analysis of the communication, security and sustainability in the three case studies.

Phd Dissertation

State-Led Housing Planning: Rule Complexity and Implementation Trade-offs

Publication Date

July 31, 2021

Abstract

California’s housing planning system seeks to address housing shortages and promote housing development in areas accessible to transit, jobs, and socioeconomic opportunities. Since 2017, the state Legislature has enacted a set of laws seeking to strengthen the housing planning system through a complex array of standards, requirements, and procedures. California’s current housing planning system is comprised of a complex housing target allocation mechanism and enforcement mechanisms to ensure that local governments effectively accommodate the development of the allocated housing units. However, the complexity of the rules will likely lead to numerous implementation challenges. This dissertation, consisting of three studies, examines the implementation of California’s current housing planning system at different levels of government and highlights the trade-offs related to the complexity of the system. The first essay draws on interview data and observations of public events and underscores the ways in which the complexity of the state’s planning rules has posed implementation challenges related to administrative efficiency, inclusive decision-making, flexibility, legal uncertainty, and legitimacy perceived by different stakeholders. The second essay compares the mechanism that the Southern California Association of Governments (SCAG) uses to allocate housing units to local governments with two simpler alternatives. Through the assessment of different allocation scenarios in the SCAG region, this essay finds evidence that a simpler allocation mechanism could potentially guide housing development to transit- or jobs- rich areas more equitably and with lower administrative burdens. The third essay turns to planning implementation at the local level and examines the trade-offs involved in directing new housing opportunities, especially subsidized housing, away from relatively poor neighborhoods. Focusing on the City of Los Angeles, this essay finds evidence that newly subsidized housing would alleviate residential crowding in single-family neighborhoods but not in relatively crowded, high poverty neighborhoods. The empirical results, however, may be driven by the growing demands for affordable housing units with the appropriate size in these neighborhoods. This dissertation reveals implementation trade-offs that are at least in part due to the complexity of the planning processes and techniques that are required by state law or promoted by government agencies. Current complex rules in place may not necessarily achieve the goal of promoting housing development equitably. Possible directions for improving state-led housing planning efforts involve simplifying the system in a way that reduces the use of administratively complex procedures and the reliance on overly technical approaches. Decision-makers should be aware of the potential trade-offs among different policy objectives and, in some cases, need to recognize that important objectives may conflict.

Phd Dissertation

Beneficial or Disruptive Change? Perspectives of Neighborhood Change in Santa Ana, CA

Publication Date

June 14, 2021

Author(s)

Abstract

This study investigates the perspectives of neighborhood change that exist among residents from varying backgrounds in neighborhood associations and community-based organizations in Santa Ana, California, a predominately low-income and Latinx community in central Orange County, California. The objective of this study is to acquire a greater understanding of why some individuals oppose some neighborhood changes, while others withdraw from changes, and others come to accept them. This study further seeks to investigate what has given rise to their distinct perspectives of neighborhood change. Results contribute to environmental psychology and neighborhood change literature by highlighting the social and psychological aspects of sustainable urban development and neighborhood change by understanding how residents from varying backgrounds feel about the change they are observing and experiencing.

Individuals from neighborhood associations (NA) and community-based organizations (CBO) in Santa Ana are the focus of this study given their active opposition to urban development since the 1970s. In this study, I detail how individuals embedded in NAs, individuals embedded in CBOs, and individuals with no group affiliation vary in their perspectives and responses to observed change in the context of sustainable urban development taking shape in Santa Ana. With qualitative research methods, I draw from environmental psychology, urban sociology, and planning literature to investigate how individuals perceive change and respond to disruptions to place. Data collected include 41 semi-structured interviews, field notes from participant observations of city council and neighborhood organization meetings, and archival documents including local newspaper articles and city government meeting minutes.

Findings demonstrate that perspectives and responses to change vary by race, class, generation, and proximity to change. Whereas individuals embedded in NAs (consisting of mostly middle-class homeowners in their 60s) are more open to changes occurring in Downtown Santa Ana, they are more resistant of changes in the form of high-density apartment units occurring in their own neighborhoods given the threat they impose to the character of their single-family neighborhoods. Individuals embedded in CBOs (consisting of mostly renters in their 20s-30s, Latinxs, and low-income residents) are more likely to resist projects that impose a threat to their place identity, especially many changes occurring in Downtown Santa Ana. Individuals from both groups provide a critical reevaluation of what change means in this era of increased sustainable development in the shape of policies, investments, and projects. Such matters highlight the opposing views and tensions related to class and race that exist among those influencing change in a city like Santa Ana and are bound to come forward in planning processes and outcomes.

MS Thesis

Calibration and validation of generalized bathtub model with boston's bluebikes data

Abstract

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. 

conference paper

Heterogeneity in Activity-travel Patterns of Public Transit Users

Abstract

Public transit is considered a sustainable mode of transport that can address automobile dependency and provide environmental, economic, and societal benefits. However, with typical temporal and spatial constraints such as fixed routes and schedules, transfer requirements, waiting times, and access/egress issues, public transit offers lower accessibility and mobility services than private vehicles and thus it is considered a less attractive mode to many prospective users. To improve the performance of transit and in turn to increase its usage, a broader understanding of the daily activity-travel patterns of transit users is fundamental. In this context, this study analyzed transit-based activity-travel patterns by classifying users via Latent Class Analysis (LCA). Using data from the 2017 National Household Travel Survey, the LCA model suggested that transit users could be split into five distinct classes where each class has a representative activity-travel pattern. Class 1 constituted employed white males who made transit-dominant simple work tours. Class 2 was composed of employed white females who made complex work tours. Employed white millennials comprised Class 3 and made multimodal complex tours. Transit Class 4 were non-white younger or older adult groups who made transit-dominant simple non-work tours. Last, Class 5 members made complex non-work tours with recurrent transit use and comprised single older women. This study provided insights regarding the variations of activity-travel patterns and the associated market segments of transit users in the United States. The results can assist transit agencies in identifying transit user groups with particular activity patterns and considering market strategies that can address their travel needs.

conference paper

An Exploratory Analysis of Alternative Travel Behaviors of Ride-hailing Users

Abstract

The emergence of ride-hailing, technology-enabled on-demand services such as Uber and Lyft, has arguably impacted the daily travel behavior of users. This study analyzes the travel behavior of ride-hailing users first from conventional person- and trip-based perspectives and then from an activity-based approach that uses tours and activity patterns as basic units of analysis. While tours by definition are more easily identified and classified, daily patterns theoretically better represent overall travel behavior but are simultaneously more difficult to explain. We thus consider basic descriptive analyses for tours and a more elaborate approach, Latent Class Analysis, to describe pattern behavior. The empirical results for tours using data from the 2017 National Household Travel Survey show that 76% of ride-hailing tours can be represented by five dominant tour types with non-work tours being the most frequent. The Latent Class model suggests that ride-hailing users can be divided into four distinct classes, each with a representative activity-travel pattern defining ride-hailing usage. Class 1 was composed of younger, employed people who used ride-hailing to commute to work. Single, older individuals comprised Class 2 and used ride-hailing for midday maintenance activities. Class 3 represented younger, employed individuals who used ride-hailing for discretionary purposes in the evening. Last, Class 4 members used ride-hailing for mode change purposes. Since each identified class has different activity-travel patterns, they will show different responses to policy directives. The results can assist ride-hailing operators in addressing evolving travel needs as users respond to various policy constraints.

policy brief

Analysis of Activity Travel Patterns and Tour Formation of Transit Users

published journal article

Perceptions of Neighborhood Change in a Latinx Transit Corridor

Abstract

Understanding how nearby residents feel about transit-induced neighborhood change remains understudied despite growing concerns over displacement and gentrification. This study analyzed 329 surveys of resident perceptions of neighborhood change and associated development near an existing commuter rail station and a planned streetcar route in Santa Ana, California, a largely low-income, Latinx community. We found residents were on average satisfied with neighborhood access to transport and amenities, and that higher neighborhood satisfaction was associated with a more positive assessment of development and neighborhood change. Living near the streetcar route was associated with more negative assessments of change, reflecting residents of these areas had heightened concerns about housing costs, displacement, and parking. Results provide planners with insights regarding support for and concerns about transit-induced neighborhood changes that can help foster more equitable and responsive development processes and outcomes.

research report

Analysis of Activity Travel Patterns and Tour Formation of Transit Users

presentation

Invited Expert Testimony in 2021 on the California ”Heavy Duty Vehicle Sector” to the Joint Informational Hearing of the California Senate Committee on Transportation and Senate Budget Subcommittee 2 on Resources, Environmental Protection, and Energy, on The California Energy Commission’s Clean Transportation Program and California’s Zero Emissions Vehicle Deployment Strategy