MS Thesis
This study will evaluate the real causes of phantom traffic jam by evaluating different continuous car-following models under different conditions. Finding the origins of these instabilities would lead to apply some control measures which may solve or minimize the stop and go traffic patterns and improve the whole road performance.
conference paper
The San Pedro Bay Ports (SPBP) of Los Angeles and Long Beach in Southern California is one of the largest port container complexes in the world, and the largest one is the United States. To decrease the air pollution associated with port operations, a number of measures have been adopted, including the Clean Trucks Program, which was introduced in 2008 to modernizing and clean up the fleet of drayage trucks serving the SPBP. The objective of this paper is to quantify the reduction in emissions attributable to the Clean Trucks Program, with a focus on Nitrogen Oxide (NOx) and Particulate Matter (PM2.5). The authors approach is innovative as it relies on micro-simulation (TransModeler) to capture the link between congestion and pollutant emissions. The authors find that the Clean Trucks Program could contribute significantly to the emissions of NOx (~27%) and PM2.5 (~25%) for all the freeway traffic in the study area. These preliminary results suggest that the Clean Trucks Program is promising, but its cost-effectiveness should be analyzed.
conference paper
Given that small fleets (defined as those with 20 or fewer vehicles) represent a considerable portion of the heavy-duty vehicle (HDV) sector, understanding their perspectives, along with those of large fleets, on zero-emission vehicles (ZEVs) and related policies is crucial for achieving the U.S. HDV sector’s ZEV transition goals. However, research focusing on small fleets or comparing both segments has been limited. Focusing on California’s drayage sector with stringent ZEV transition targets, this study investigates the awareness and perceptions of small and large fleet operators on ZEV technologies and policies established to promote ZEV adoption. Using a fleet survey, we obtained 71 responses from both small and large fleets. We employed a comprehensive exploratory approach, utilizing descriptive analysis, hypothesis testing, and thematic analysis. Findings reveal that both segments generally rated their ZEV knowledge as close to neutral, with about a third reporting limited awareness of the ZEV policy. Both segments highlighted various adoption barriers, including challenges with infrastructure, costs, and operational compatibility. Business strategies under the ZEV policy differed significantly: small fleets planned to delay or avoid ZEV procurement, with some considering relocation, while large fleets were more proactive, with many already having procured or preparing to procure ZEVs. Both segments voiced concerns about the disproportionate impact on small fleets. The findings enhance our understanding of equity issues in ZEV adoption across fleet segments and offer valuable insights for policymakers committed to a more equitable distribution of the impacts.
published journal article |
Apr 2024
working paper
The paper reports on the analysis of violation and crash data as part of an evaluation of the impact on traffic safety of the San Diego Photo Red Light Enforcement System. The system was found to have resulted in a statistically significant reduction in the number of red light running violations. The decreases in violations occurred at almost all camera enforced intersections and the decreases continued, at a diminishing rate, throughout the period the cameras were operated. The impact on traffic safety was more complex. For traffic traveling in the enforced direction at intersections with red light cameras, crashes attributable to red light running decreased after implementation to approximately 60 percent of pre-enforcement rates, while rear end crashes increased to approximately 140 percent of pre-implementation levels. These before-and-after changes in crash rates were statistically significant, while there were no significant changes in crash rates for traffic traveling in directions not covered by the red light cameras. In addition, it is concluded that photo enforcement was more effective in reducing crashes at intersections where through movement was enforced, than where left turns were enforced.
published journal article
A study was conducted to determine how demand for clean-fuel vehicles and their fuels is likely to vary as a function of attributes that distinguish these vehicles from conventional gasoline vehicles. For the purposes of the study, clean-fuel vehicles are defined to encompass both electric vehicles and unspecified (methanol, ethanol, compressed natural gas or propane) liquid and gaseous fuel vehicles, in both dedicated or multiple-fuel versions. The attributes include vehicle purchase price, fuel operating cost, vehicle range between refueling, availability of fuel, dedicated versus multiple-fuel capability and the level of reduction in emissions (compared to current vehicles). In a mail-back stated preference survey, approximately 700 respondents in the California South Coast Air Basin gave their choices among sets of hypothetical future vehicles, as well as their choices between alternative fuel versus gasoline for hypothetical multiple-fuel vehicles. Estimates of attribute importance and segment differences are made using discrete-choice nested multinomial logit models for vehicle choice and binomial logit models for fuel choice. These estimates can be used to modify present vehicle-type choice and utilization models to accommodate clean-fuel vehicles; they can also be used to evaluate scenarios for alternative clean-fuel vehicle and fuel supply configurations. Results indicate that range between refueling is an important attribute, particularly if range for an alternative fuel is substantially less than that for gasoline. For fuel choice, the most important attributes are range and fuel cost, but the predicted probability of choosing alternative fuel is also affected by emissions levels, which can compensate for differences in fuel prices.
working paper
This study examines electronic integration in logistics supply chains using the non-integrated US-international air cargo industry as a case study. We ask what impact electronic integration has on interorganizational task performance, and hypothesize about factors limiting the effectiveness of electronic integration. Surprisingly, our study does not find evidence of direct impacts of electronic integration on performance though it does find evidence of indirect impacts of information systems use and performance. The findings suggest that the use of electronic integration as a strategy to improve operational performance across firms is limited by the nature of the interorganizational task, environmental dynamism, and the power relationship between firms in the supply chain.
research report
In October 2021, the Los Angeles Count Metropolitan Transportation Authority (LA Metro), in collaboration with other regional transit operators and multiple school districts across the county, launched the GoPass pilot program to offer free transit passes to K-14 students, which became permanent in early 2024. Students in a high school district in the Greater Los Angeles area were surveyed to determine the reasons students decided to participate in GoPass and how the students subjectively valued their travel preference. Students were less likely to participate in the GoPass program if they had the use of a car for trips to school but more likely if they had the option to take transit for trips leaving school. Student demographics did not play a large role in whether they participated in GoPass. Students highly value cars and trip amenities, such as onboard Wi-Fi. They subjectively value reduced travel time at $71/hour, similar to other studies among adults, but valued reduced waiting time at $98/hour, again consistent with other studies that find a high relative value for shorter waiting time. Students are not likely to be persuaded to take transit merely by making it free. Instead, school districts may consider increasing the cost for campus parking permits and reducing the number of campus parking spaces to encourage greater use of transit and shared travel modes.
published journal article
Phd Dissertation
The past 30 years have witnessed a gradual expansion in the missions of many universities, and in the ways in which they contribute to local and regional economic development. While teaching and research continue to serve as the foundational core of most university missions, increased attention has been afforded to how universities, by their presence and functions, influence the spatial geographies of neighborhoods, cities, and regions. This dissertation research explores the changing roles of research universities in small and medium-sized metropolitan areas with an emphasis on their impacts across the different geographical scales by investigating associations between university presence and (1) growth in foreign-born populations; (2) the attraction and retention of highly educated residents; and (3) student-driven neighborhood change dynamics. The findings of this dissertation extend previous studies emphasizing the increasing importance of higher education institutions to economic development activities at various scales. Results from metropolitan area level analyses demonstrate that counties with large research universities were associated with an increase in foreign-born residents following the 1990 Immigration and Naturalization Act, as well as an increase in highly educated residents in the 2000-2014 period. More specifically, while findings revealed that the presence of research universities generate significant spatial spillovers of highly educated residents from university host counties to metropolitan levels, there was little evidence of such spatially-explicit dynamics occurring amongst foreign-born residents. Furthermore, findings from neighborhood-level analyses indicated that proximity to large research university campuses may play an outsized role on the likelihood of neighborhoods undergoing studentification (i.e., student-driven neighborhood change) in the 2000-2014 period. These results may be indicative of a bifurcation of neighborhoods in university-dominant counties into wealthy and highly educated renter populations situated near the university campus, and relatively less wealthy and less educated homeowners residing on the further away from the campus or on the periphery of the county. By exploring university contributions beyond the spheres of research, teaching, and service contributions, this dissertation presents scholars, urban planners, and policymakers with a more comprehensive portrait of the relationship between universities and their host communities. The evidence of this work suggests that the evolving role of higher education institutions, including their role as gateways for new populations, should be reflected in policymaking which seeks to leverage the locational advantages of research universities for city building or revitalization efforts. Further, policymakers and planners should also be cognizant that scale matters when considering how higher education institutions can better serve their surrounding communities. The contributions of research universities should not be thought of as monolithic or uniform, but should rather be seen as presenting different opportunities and challenges at different geographical levels.
book/book chapter
