published journal article
Phd Dissertation |
Jun 2003
research report
In 2017, California passed Senate Bill 1 (SB1) to bolster transportation infrastructure funding. Using data primarily from the California Department of Transportation (Caltrans)’s official SB1 progress reports, we analyze the severity of cost overruns, delays, and cancellations across SB1 Transportation Projects. Although events such as the COVID-19 pandemic likely caused some of these negative outcomes, our statistical models show consistent patterns of overruns associated with fiscal periods, programs, and geographic locations. Our results indicate that the common 20% contingency is generally insufficient, indicating the need for better risk estimation in project planning. We also suggest amplifying data transparency on project performance and re-evaluating project selection criteria to avoid rewarding underestimation of project costs and duration and penalizing accurate estimation.
policy brief |
Oct 2024
working paper
Over the past several years, the private vehicle has become the predominant mode of travel to school while walking and bicycling rates have decreased. Some suggest that this change in travel behavior contributes to negative health outcomes in children, including increased rates of 1) overweight/obesity through inactivity and 2) pedestrian and bicyclist fatality and injury. A series of recent policies and programs directly attribute the change in travel behavior to school to the urban form of communities. Limited research exists to support this hypothesis, however. The fundamental questions of whether and how urban form impacts a child’s trip to school must to be answered in order to develop effective interventions aimed at increasing rates of walking and bicycling activity and safety.
The research proposes a conceptual framework to examine the nature and shape of the relationships between urban form; interpersonal, demographic and social/cultural factors; parental decision-making and a child’s travel to school. Using parent survey data on children’s travel to school and urban design assessments from twelve elementary school neighborhoods, the relative influence of urban form on the mode choice to school was first determined. Results indicate that urban form elements such as street lights and street widths do affect the probability of a child walking or bicycling to school; however, the affect of these elements is modest compared to other influential variables such as the perceived convenience of driving, country of birth, family support of walking behavior, reported traffic conditions in the neighborhood and perceived distances between home and school.
A second analysis examined how urban form and children’s travel behavior relate by testing the hypothesis of an indirect relationship. The findings show that parent’s feelings of neighborhood safety, traffic safety and/or household transportation options do not intervene in the relationship between urban form and children’s travel behavior. Socio-demographic characteristics and parent’s attitudes toward travel, however, may modify the strength of the relationship between urban form and children’s travel behavior.
The results of this study advance the discussion on relationships between urban form, transportation and health and inform policy and practice of the best targets for future planning interventions.
conference paper
Light-duty vehicles are responsible for over 16% greenhouse gas (GHG) emissions in the United States. Human driving behavior has a significant impact on vehicle efficiency, the emission of GHG and primary pollutants, and safety. With environmental health in mind, both academia and industry have the opportunity to develop advanced sensor and complementary control technologies to manage the human role. To explore this hypothesis, the research reported herein began with a comprehensive study of demonstration projects and academic publications which test and evaluate modern technologies to mitigate threats associated with safety and efficiency. The research identified the environmental signals to detect, the corresponding sensors to detect these signals, and the sensor technologies to study in greater depth. Of all the sensor technologies, vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications technologies emerged as the most promising. A major requirement identified is a planning tool designed to assess advanced vehicle sensor technologies on traffic flow, fuel economy, and emissions. In response, a major focus of the research was then directed to (1) developing the Fuel Economy and Traffic of Connected Hybrids (FETCH) planning tool, and (2)Â?evaluating the utility of FETCH for a simple V2V-enabled automatic re-routing control on a custom roadway. The major outcomes of this research work are (1) the FETCH tool, (2) a research plan for utilizing FETCH to explore the variety of scenarios evolving for the advanced control of hybrid vehicles, and (3) an example research result of FETCH.
conference paper
conference paper
working paper
This project will further adapt and enhance the previous research of relevance to event-based Advanced Traveler Information Systems (ATIS) and implement the algorithms for traffic management in Anaheim. The implementation involves the Caltrans-UCI ATMS research testbed framework at the UCI Institute of Transportation Studies, as well as the physical hardware available for communication to the city of Anaheim. The analytical algorithms proposed for use here include those for static and dynamic traffic assignment. and the modeling schemes used are the result of previous PATH and Testbed research projects on traffic simulation and driver behavioral response to information. The essential part of algorithmic research will be to adapt the network optimization algorithms to generate traffic rerouting plans, which involve aggregation of network paths and their translation to a format usable for changeable message signs existing in Anaheim. as well as other event-based information supply hardware. The implementation plan envisages a framework that is usable by the city for event-based congestion management, but its useis left to the city’s decision. Key words: Advanced Traveler Information Systems, Optimal Routing, Dynamic Traffic Assignment, Changeable Message Signs
research report |
Sep 2001
Phd Dissertation
This dissertation proposes a heuristic theoretical framework for understanding dynamics that impact environmental health including social/built environmental settings, individual residents’ behavioral patterns, location activity spaces (LAS), environmental quality, exposure, and health outcomes. I examined the relationships between factors included in the framework based on individuals’ LASs, and represent a hypothetical geographic boundary in which an individual is expected to spend his/her time in daily life. In addition to the individual level exposure, I characterized built environmental quality for subsidized housing neighborhoods in Los Angeles and Orange Counties, which have not been the focus of previous affordable housing studies. In Chapter 2 and Chapter 4, I empirically demonstrated the framework for residents in neighborhoods near the Expo Right Rail Transit line and the Boyle Heights community in Los Angeles. With OLS regression analysis, I found that bigger LAS were associated with lower walkability, more non-residential land use, higher transit stop density, shorter length of residency, working out of home, and higher income. I examined the relationship between the probability of a census block group (BG) having at least one subsidized unit and associated BG built environmental qualities. Based on logistic regression models, I found that subsidized housing units tended to be located in BGs with better transit access, lower walkability, more mixed-use, and lower air pollution concentrations.
published journal article
While the geography of land use control is shaped by various forces operating at multiple levels, how land use is regulated in the U.S. has been examined with a narrow focus on either intraregional variation (within a single region) or aggregate differences between regions. This article presents an investigation of the geographical distribution of land use control with explicit consideration of both local and regional factors. Using data from two nation-wide surveys and other sources of information, it shows that substantial variation exists not only between regions but also within regions, calling for more attention to what matters and at what level. It is also found that the multilevel determinants of land use regulations are not uniform across regulation types. While low-density zoning is largely determined by local factors with limited interregional variation, a higher level of heterogeneity between regions is detected for impact fees and affordable housing requirements.
published journal article