conference paper
policy brief
This research was motivated by the need to better understand how the hazard preparedness and resilience strategies of California’s public transportation system can be improved through integration with social and safety infrastructure. The study focuses on a specific type of social infrastructure called ‘Resilience Hubs’, which are community-operated and community-serving facilities that support residents in accessing resources and support during both everyday conditions and extreme events. Considering the potential of these hubs to enhance resilience and safety for historically marginalized individuals, public sector decision makers must understand the function and impact of Resilience Hubs and ensure access to them. To better understand the role of social infrastructure like Resilience Hubs in supporting safety and hazard preparedness, as well as its integration with public transit, the researchers collaborated with one of Los Angeles’ first Resilience Hubs as of 2021: the Boyle Heights Arts Conservatory (BHAC). In partnership with the BHAC and the local non- profit Climate Resolve, the researchers collected data through three listening sessions with a total of 26 residents of Boyle Heights, Los Angeles, with connections to the BHAC. The research sought to amplify how residents of Boyle Heights experience cascading urban vulnerabilities and resilience, both in terms of physical and social infrastructure, as well as the improvements they envision for public transit integration with social infrastructure to enhance the resilience of both systems.
presentation |
Mar 2025
research report |
Jan 2025
published journal article
Recent literature has shown that volatile organic compound (VOC) emission inventories for urban regions may be substantially underestimated. In particular, non-transportation sources including volatile chemical products (VCP) are increasing in relative importance due to both the current and historical focus on controlling transportation emissions. These findings have major implications for photo-chemical air quality modeling used to determine appropriate and effective regulatory controls to meet limits for primary and secondary pollutants. Using a regional air quality model, we quantify the changes in ozone and fine particulate matter (PM2.5) simulated for updated VOC emissions reported in the recent literature relative to a baseline inventory for California. Results show that simulated maximum 8-hr ozone concentrations could increase by 17.4 ppb in summer and by 15.6 ppb in winter, and the 24-hr maximum PM2.5 could increase by 7.8 mu g/m(3) in winter. Impacts reflect differences in the spatial location of VCP source emissions relative to those for transportation. However, compared to measurement data, model performance is not substantially improved by the adjustment of VOC emissions of current sources. In brief, augmented VOC emission inventories impact simulated concentrations of pollutants, but may not improve the performance of models used for the design of emission control policy without more refined representation of missing VCPs sources in the inventory.
published journal article
A primary goal of intelligent transportation systems is to improve road safety. The ability of vehicles to communicate is a promising way to alleviate traffic accidents by reducing the response time associated with human reaction to nearby drivers. Vehicle mobility patterns caused by varying traffic dynamics and travel behavior lead to considerable complexity in the efficiency and reliability of vehicular communication networks. This causes two major routing issues: the broadcast storm problem and the network disconnection problem. In this article we review broadcast communication in vehicular communication networks and mechanisms to alleviate the broadcast storm problem. Moreover, we introduce vehicular safety applications, discuss network design considerations, and characterize broadcast protocols in vehicular networks.
Phd Dissertation |
Jan 2010
conference paper
A new framework for inter-regional commodity flow forecasting is presented to improve estimates of freight demand for inter-regional and statewide transportation models. The Structural Equations for Multi-Commodity OD Distribution (SEMCOD) model is based on simultaneous direct demand equations with structural relationships between dependent and independent variables of the model. SEMCOD is a flexible model that integrates the generation and distribution steps in conventional four-step demand models. This integration provides consistent estimates for elasticity analysis of effective factors for freight flows at the OD level and for productions and attractions at the zone level. Also, the model is sensitive to policies that increase or decrease generalized transportation cost, not only for flow distribution but also by measuring the change in marginal production and attraction of each zone. Unlike gravity-type models, this framework provides the opportunity to identify homogenous clusters of ODs and to more accurately estimate parameters for each cluster. The proposed model is estimated using the Freight Analysis Framework (FAF3) and other publicly available data sources for 15 commodity groups. Elasticity of different factors on production, attraction and flow of different commodity groups with respect to industry specific employment, population, industrial GDP, variables related to consumption and production of energy and land use variables, are studied. Considering cross relationships between supply chains of different commodity groups in the model significantly improved the fitness of the model. The fitness measures confirm satisfactory performance of the model.
published journal article
published journal article
published journal article
In spite of their substantial number in the U.S., our understanding of the travel behavior of households who do not own motor vehicles (labeled “carless” herein) is sketchy. The goal of this paper is to start filling this gap for California. We perform parametric and non-parametric tests to analyze trip data from the 2012 California Household Travel Survey (CHTS) after classifying carless households as voluntarily carless, involuntarily carless, or unclassifiable based on a CHTS question that inquires why a carless household does not own any motor vehicle. We find substantial differences between our different categories of carless households. Compared to their voluntarily carless peers, involuntarily carless households travel less frequently, their trips are longer and they take more time, partly because their environment is not as well adapted to their needs. They also walk/bike less, depend more on transit, and when they travel by motor vehicle, occupancy is typically higher. Their median travel time is longer, but remarkably, it is similar for voluntarily carless and motorized households. Overall, involuntarily carless households are less mobile, which may contribute to a more isolated lifestyle with a lower degree of well-being. Compared to motorized households, carless households rely a lot less on motor vehicles and much more on transit, walking, and biking. They also take less than half as many trips and their median trip distance is less than half as short. This study is a first step toward better understanding the transportation patterns of carless households.
conference paper |
Jan 2018
published journal article |
Dec 2017
published journal article |
Nov 2019
policy brief |
May 2020
research report |
May 2018
published journal article
conference paper