published journal article
conference paper
published journal article
(A) method is developed to determine how crash characteristics are related to, traffic flow conditions at the time of occurrence. Crashes are described in terms of the type and location of the collision, the number of vehicles involved, movements of these vehicles prior to collision, and severity. Traffic flow is characterized by central tendencies and variations of traffic flow and flow/occupancy for three different lanes at the time and place of the crash. The method involves nonlinear canonical correlation applied together with cluster analyses to identify traffic flow regimes with distinctly different crash taxonomies. A case study using data for more than 1000 crashes in Southern California identified twenty-one traffic flow regimes for three different ambient conditions: dry roads during daylight (eight regimes), dry roads at night (six regimes), and wet conditions (seven regimes). Each of these regimes has a unique profile in terms of the type of crashes that are most likely to occur, and a matching of traffic flow parameters and crash characteristics reveals ways in which congestion affects highway safety. (C) 2003 Elsevier Ltd. All rights reserved.
MS Thesis
Results from the 2000 SCAG Post-Census Regional Travel Survey and the 2010-2012 California Household Travel Survey are used to study the demographics and characteristics of Imperial, Los Angeles, Orange, Riverside, San Bernardino, and Ventura counties. Graphs for each county are created to show pertinent data to transportation applications, such as the average number of vehicles a household owns or how many trips certain individuals make in one day. Studying both sets of data gives perspective on how the SCAG region has evolved over 12 years. The overwhelming majority of trips are still traveled by personal vehicle, despite walking trips seeing an increase over 2000, and trips are more frequent overall.
working paper
Two recent technological events should be examined more closely for their applicability to ATMIS and other ITS systems. First, the recent rise of wireless LAN protocols such as 802.11b should be studied for use in a vehicle context. Second, the rise and fall of Napster, followed by increased development on more decentralized protocols such as Gnutella and Freenet are leading to an increasingly robust peer-to-peer platforms. This paper argues that peer-to-peer communication and local area wireless networks should play a central role in any system to distribute traveler information services. Instead, the National ITS Architecture makes no mention of peer-to-peer information exchange, relegating local area wireless connections to vehicle control.
working paper
This research has two objectives. The first objective is to explore the use of the modeling tool called “latent structural equations” (structural equations with latent variables) in the general field of travel behavior analysis and the more specific field of dynamic analysis of travel behavior. The second objective is to apply a latent structural equation model in order to determine the causal relationships between income, car ownership, and mobility. Many transportation researchers might be unfamiliar with latent structural equation modeling, which is also known as “latent structural analysis,” “causal analysis,” and “soft modeling.” However, most researchers will be quite familiar with techniques that are special cases of latent structural equations: e.g., conventional multiple regression and simultaneous equations, path analysis, and (confirmatory) factor analysis. Furthermore, recent advances in estimation techniques have made it possible to incorporate discrete choice variables and other non-normal variables in structural equations models. Thus, probit choice models (binomial, ordered, and multinomial) can be incorporated within the general model framework. The empirical analysis reported here involves dynamic travel demand data from the Dutch National Mobility Panel for the three years 1984 through 1986. All variables in the model, with the exception of income level in the first year, are endogenous: income is treated as an ordinal (four category) variable; car ownership is treated as either an ordinal (ordered probit) or a categorical (multinomial probit) choice variable; and mobility, in terms of car trips and public transport trips, is treated as two censored (tobit) continuous variables. The model fits the data well, but only scratches the surface of the potential of latent structural equation modeling with panel data. Some possible extensions are outlined.
research report
This report documents the work conducted by the Institute of Transportation Studies at UC Irvine (ITS-Irvine) for the San Diego Association of Governments (SANDAG) under contract 5005881 between February 20th, 2020 and November 30th, 2020. This project focused on providing SANDAG with the latest research, data, and tools that can be used to support the development of the SANDAG 2021 Regional Transportation Plan (RTP), with a focus on identifying how the advances in technology, coupled with public policy can enable the region to rethink and to maximize the coordination between land use and transportation planning and, in particular, operationalizing off-model methodologies for use in SANDAG’s submission of the Sustainable Communities Strategy (SCS) methodology to the California Air Resources Board (CARB).
conference paper
This paper provides extensions to the Household Activity Pattern Problem (HAPP) to help move existing formulations from a laboratory prototype toward a more usable activity-based demand modeling product. Previous research on HAPP has been based on a pickup and delivery problem with time window constraints (PDPTW), which does not lend itself easily to application compatible with an activity-based forecasting model. Meanwhile, other research on activity based modeling lacks of the integration of household decisions on time of day arrival, activity duration and traffic congestion effect on travel. For the demand side, the authors propose to incorporate time-of-day factors influencing both activity arrival and activity duration utility into HAPP as decision variables. Alternatively, for the supply side, the authors extend HAPP to capture the time-of-day (TOD) differences in travel times and costs to form the travel time-dependent utility household activity pattern problem model (TUHAPP). In their synthetic examples, the authors demonstrate how TUHAPP handles impacts of policy changes on peopleâ??s departure and activity duration decisions and how traffic congestion can change peopleâ??s travel agendas.
MS Thesis
Plug-in fuel cell electric vehicles (PFCEVs) combine features of battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs). With a 40-mile battery electric range (BER), the PFCEV provides unusually efficient driving. The BER also affords convenient recharging. The fuel cell and hydrogen fuel facilitate long range and quick refueling, removing range anxiety. With a small battery and fuel cell, the PFCEV maintains weight low and efficiency high. This thesis uses California as a case study of PFCEV deployment, due to regulations that make it the first deployment area of alternative vehicle technology, using vehicle and electric grid simulation tools, travel survey and census data, and geographic information system (GIS) software. If all passenger vehicles in California today were PFCEVs, the hydrogen required would be significantly less than current hydrogen production for petroleum refining in California, and the electricity used would be 19% of California’s current total demand. The BER capability leads to far fewer hydrogen fueling stations needed to fuel PFCEVs compared to non-plug-in FCEVs: 93 hydrogen stations are required compared to 1,651. PFCEVs also lead to the most GHG and CAP emissions reductions of any advanced alternative vehicle. Furthermore, this is done at the lowest cost per emissions reduced. PFCEVs are an attractive candidate as the principal vehicle owned by the majority of the motoring public in the electric vehicle era.
book/book chapter