Phd Dissertation

An Analysis of the Impact of an Incident Management System on Secondary Incidents on Freeways – An Application to the I-5 in California

Abstract

Accidents are the largest source of external costs related to transportation in the United States with annual costs estimated to exceed $200 billion per year. Incidents also create traffic backups and delays that can result in secondary incidents (i.e., collisions that occur as a result of other incidents). Although incident management has received a lot of attention from academics and practitioners alike, secondary incidents have so far been somewhat neglected. The main purpose of this dissertation is to investigate empirically whether the implementation of changeable message signs (CMS), which are one Intelligent Transportation System tool, can reduce secondary collisions. After reviewing previously published methods for estimating secondary accidents, I implement a Binary Speed Contour Map approach to detect secondary incidents using PeMS data. I also estimate the extra time lost to congestion because of incidents. My study area is a portion of Interstate 5 that stretches 55 miles from the Mexico-US border to Northern San Diego County, CA. This freeway portion has an x average annualized daily traffic volume of 230,000 vehicles. My unique dataset includes incident data for 2008 combined with detailed weather data, elements of freeway geometry, and information about CMS usage. I identify a total of 9,003 incidents in my study area in 2008. Using the BSCM approach, I find that 3.7 percent of collisions were secondary incidents. Moreover, my statistical model shows that incidents occurring during evening peak hours on Fridays or during midday on weekends are more likely to result in secondary crashes as do incidents with injuries or fatalities, incidents that involve more vehicles or trucks, or incidents that take place when the pavement is wet. Conversely, secondary crashes are less likely to occur in areas with a complex geometry (perhaps because drivers are more cautious there) or for incidents taking place on the side of the freeway. More importantly, changeable message signs (CMS) decrease the occurrence of secondary crashes. The maximum effectiveness of a CMS is approximately 11.75 miles for a range of 23.6 miles. Finally, annual incident-related congestion is approximately 1.9 hours per freeway vehicle, which represents five percent of the 37 hours of annual traffic delay experienced by the average San Diego motorist.

conference paper

Development of a real-time on-road emissions estimation and monitoring system

Abstract

Transportation has been a significant contributor to total greenhouse gas and criteria air pollutant emissions. Emission mitigation strategies are essential in reducing transportation’s impacts on the environment. In order to effectively develop and evaluate on-road emissions reduction strategies, it is important to have an information support system which can estimate and monitor on-road emissions under real world traffic operations. Emission data provided by such a system can be used to identify emission hot spots and their causes, and to develop and evaluate reduction strategies. In this paper, a system is developed to estimate and monitor operational on-road emissions with high accuracy and resolution in real time. The two sets of critical information for emission estimation, vehicle mix and vehicle activity, are directly generated from traffic detection using inductive vehicle signature technology. An initial implementation on a section of the I-405 freeway at Irvine, California is demonstrated. With more widespread deployment, the system can be used to perform before-and-after evaluation of certain mitigation strategies, to develop time sensitive optimal traffic control strategies with the purpose to control emissions, and to provide high fidelity greenhouse gas and air quality information to policymakers, researchers, and the general public.

Phd Dissertation

Of Planes, Trains and Automobiles: Market Structure and Incentives for a more Efficient, Cleaner and Fairer Transportation System

Publication Date

August 24, 2011

Author(s)

Abstract

The unifying theme of this dissertation’s three applications of economics to transportation is an attempt to make transportation more efficient, environmentally friendlier and fairer. In my first essay, I apply game theory and the notion of Cournot equilibrium to transportation. I compare two networks, hub-and-spoke and a point-to-point network, which is served by two non-cooperative transportation firms. I find that the way in which two firms set their respective network, either direct indirect service, has an effect on their costs and profits. In my second essay, I analyze the ownership of hybrid electric vehicles by U.S. households using the 2009 National Household Travel Survey to understand the impact of various government policies aimed at increasing hybrid vehicle ownership, such as granting access to high-occupancy vehicle lanes, tax credits, and parking incentives. I use a logit model; explanatory variables include socio-economic characteristics, along with urban form, as well as policy variables. Understanding which policies are most cost-effective at fostering HEV ownership would allow policy makers to make effective use of public resources. 2 In my third essay, I address equity in transportation by stratifying the NHTS into three income groups: low-income, middle-income and upper-income. The purpose is to determine whether income affects travel behavior. I analyze questions in the 2009 NHTS that were not available in previous NHTS surveys. These questions inquire about internet use, medical condition and physical activity. I also estimate a series of logit models and find that those living in poverty and who report having a medical condition are more likely to make medical trips. Upper-income individuals are more likely to report social and recreational trips, meal and trips labeled as “other.” Analyzing trips by income is important from an equity standpoint when allocating scarce public funds for transportation projects, since it tells us what income groups are likely to be affected by specific transportation projects.

Phd Dissertation

Assessing Benefits and Costs of Urban Environmental Attributes in a Hedonic Framework: Three Southern California Case Studies

Abstract

This dissertation research focuses on understanding benefits or costs of some urban amenities and disamenities using the Hedonic Pricing (HP) method. It includes three Southern California case studies where different hedonic models (fixed effects, spatial Durbin model, and geographically weighted regression) are estimated to obtain unbiased and consistent parameter estimates. In the first case study, I analyze 20,660 transactions of single family detached houses sold in 2003 and 2004 in the city of Los Angeles, CA, to estimate the value of urban trees, irrigated grass, and non-irrigated grass areas. I rely on fine-grained hedonic models with many covariates to control for unobserved neighborhood characteristics. I find that Angelenos like lawns: 78 percent of the properties examined would gain value with additional irrigated grass in their neighborhood and even more (83 percent) on their parcel. However, additional parcel trees would decrease the value of almost half (46 percent) of the properties examined and they would have only a small positive impact on most of the others. By contrast, additional neighborhood trees would slightly increase the value of over 80 percent of the properties analyzed. This suggests that while Los Angeles residents may want additional trees, they are unwilling to pay for them. These results have implications for urban tree planting programs that rely primarily on private property owners. The second case study quantifies the impact of urban green spaces on the value of 1,197 multifamily buildings sold in 2003-2004 in the city of Los Angeles, California; these green spaces are either on their parcels or in their vicinity (an area 200 meters outward of each parcel boundary). It is necessary to examine multifamily houses separately because they belong to a different market. To assess the robustness of the results, I contrast a spatial Durbin model with a geographically weighted regression model and conduct an extensive sensitivity analysis. I find that increases in grassy areas either on the parcels of multifamily buildings or in their vicinity would typically not enhance their value, and neither would more parcel tree canopy cover (TCC); by contrast, most multifamily properties would benefit from an increase in vicinity TCC. These results suggest that most multifamily building owners have no incentives to increase the tree canopy cover or the grassy areas on their properties. In the third case study, I investigate the impact of freeway traffic on property values using hedonic pricing models, with a particular interest for truck traffic. I analyze 4,715 sales of single family houses that took place in 2003 and 2004 in part of the busy transportation corridor that links the Ports of Los Angeles and Long Beach to downtown Los Angeles. These houses are located at least 200 meters from the nearest arterial road to filter out the impact of traffic on arterial roads. In order to minimize the risk of omitted variable bias and spatial autocorrelation, I estimate a fine-grained fixed effects model. I find that a one percent increase in the proportion of truck traffic could decrease the value of a $420,000 house located between 100 and 400 meters from the nearest freeway by between $2,000 and $2,750. These results are important for policy makers and owners of single family houses located close to freeways as the ports of Los Angeles and Long Beach are forecasting sharp increases in drayage truck activity as the economy recovers.

MS Thesis

Understanding travel behavior and vehicle emissions from GPS and diary data an application to Southern California

Abstract

The purpose of this thesis is to explore the impact of socio-economic characteristics of drivers on travel behavior and on vehicular emissions of various air pollutants using microscopic data. My starting dataset was collected by SCAG in 2001 and 2002 during their post 2000 Census Regional Travel Survey. Of the 16,939 households who answered the survey, 297 provided self-reported 24-hour travel diary data and detailed GPS data for their vehicles, which was instrumented for SCAG’s survey. After selecting 100 out of these 297 households based on their socio-economic characteristics and the completeness of their answers, I relied on 2003 imagery in Google Earth to match diary and GPS data. An extensive clean-up of this dataset yielded a sample of 701 trips, for which I estimated emissions of CO, CO₂, NOx, HC, PM₁₀, and PM₂.₅ using OpMode in EPA’s MOVES2010 (Motor Vehicle Emissions Simulator) from second-by-second GPS travel data. A statistical analysis of the results reveals that men make longer trips than women, although the difference in their emission rates is not statistically significant. Moreover, people 60 or older are the greenest drivers: their driving patterns are more environmentally benign because they accelerate/decelerate less than younger people. Finally, I found significant differences in emission rates based on different household income levels.

MS Thesis

Exploratory ideas for projecting the growth of alternative fuel vehicles : an ecological perspective

Abstract

The rise of alternative fuel vehicles has had an impact on vehicle choice in recent years. The acceptance and growth of these vehicles is dependent upon many factors. In this thesis we present some ideas drawn from analogies to ecology to help explain a possible demand towards alternative fuel vehicles. More specifically, using basic growth and decay rates of species populations, we present some preliminary analysis regarding how ecological modeling may relate to the growth of hydrogen and battery electric vehicles. We build upon the dynamics of the ecology equations to postulate potential vehicle growth patterns. We generate synthetic data to demonstrate potential applications of the analogous models for real world scenarios and to predict possible outcomes. Additionally, we look at migration probabilities between different vehicle population areas to see how vehicles travel on a limited range, as well as examine a mutualism dynamic that could possibly exist between vehicles and their refueling or charging stations. It is emphasized that the work presented here is exploratory in nature, and that any actual application of the models that are developed is well beyond the scope of this thesis. Rather, our purpose is only to identify and demonstrate certain aspects of ecological modeling that may shed light on the potential for alternative fuel vehicles to gain an appreciable market share of the current internal combustion vehicle marketplace.

working paper

The influence of emissions specific characteristics on vehicle operation: A micro-simulation analysis

Abstract

The goal of this paper is to predict the fraction of time vehicles spend in different operating conditions from readily observable emission specific characteristics (ESC), which include geometric design, roadway environment, traffic characteristics, and driver behavior. We rely on a calibrated micro-simulation model to generate second-by-second vehicle trajectory data and use structural equation modeling to understand the influence of observed link ESC on vehicle operation. Our results reveal that 67 percent of link speed variance is explained by emission specific characteristics. At the aggregate level, geometric design elements exert a greater influence on link speed than traffic characteristics, the roadside environment, and driving style. Moreover, the speed limit has the strongest influence on vehicle operation, followed by facility type and driving style. This promising approach can be used to predict vehicle operation for models like MOVES, which was recently released by the Environmental Protection Agency.

Phd Dissertation

Essays in Industrial Organization

Publication Date

June 14, 2011

Author(s)

Abstract

Three research papers, all broadly focused on industrial organization, comprise the chapters of this dissertation. Although all these papers address market inefficiencies that arise in various industry setting, the first paper differs in theme and scope from the rest of the dissertation. The first chapter, “Switching costs and entry in the mortgage industry”, investigates the impact of switching costs and entry on the interest rate spread in the mortgage industry. I use enactment of anti-predatory lending laws across the U.S. to measure a reduction in borrowers’ switching costs. The empirical findings show that both entry and interest rate spread rise with the advent of these laws because these laws enable low-quality applicants to obtain financing more easily than before. The results suggest that lower switching costs exacerbate the adverse selection problem, so policies that reduce these costs may not produce clear benefits. The second chapter, “Information leakage and stability of research joint ventures in a differentiated product market”, analyzes the impact of information leakage on research Joint venture’s (RJV) stability and R&D expenditure in a heterogeneous product market. Firms solve their problem in three stages: in the first stage firms decide whether to join a RJV, in the second stage firms decide on the level of information sharing, and in the final stage firms engage in Cournot competition. Main results indicate a U-shaped curve between venture’s size and product differentiation when leakage is high. This research can offer a better understanding of RJVs and provide insight into policies and actions necessary to promote R&D and better flow of information in the innovation sector. The third chapter, “The impact of information leakage and product differentiation on the research joint venture’s size and R&D”, empirically examines theory set forth in the second chapter. The study uses data on RJVs from the NIST’s ATP program. As a measure of information leakage, we use a percentage of all patent litigation cases within a RJV that are valid. The main results reveal that information leakage is not a determining factor in ventures choice to include other firms and engage in cooperative R&D.

Phd Dissertation

Probabilistic Learning for Analysis of Sensor-Based Human Activity Data

Abstract

As sensors that measure daily human activity become increasingly affordable and ubiquitous, there is a corresponding need for algorithms that unearth useful information from the resulting sensor observations. Many of these sensors record a time series of counts reflecting two behaviors: 1) the underlying hourly, daily, and weekly rhythms of natural human activity, and 2) bursty periods of unusual behavior. This dissertation explores a probabilistic framework for human-generated count data that (a) models the underlying recurrent patterns and (b) simultaneously separates and characterizes unusual activity via a Poisson-Markov model. The problems of event detection and characterization using real world, noisy sensor data with significant portions of data missing and corrupted measurements due to sensor failure are investigated. The framework is extended in order to perform higher level inferences, such as linking event models in a multi-sensor building occupancy model, and incorporating the occupancy measurement from loop detectors (in addition to the count measurement) to apply the model to problems in transportation research.

Phd Dissertation

The Interplay of Urban Traffic Route Guidance, Network Control and Driver Response: A Convergent Algorithmic and Model-based Framework

Abstract

Much effort has been made in the past on the supply side to relieve road traffic congestion which undermines the mobility in urban networks and brings heavy social costs, but building additional roadway capacity is no longer considered a viable option. A better alternative is the efficient management of existing networks, for which we can envisage new possibilities that emerge in light of the recent increase in the use of private providers’ digital map and traffic information systems. These systems have evolved mostly without much public sector influence, but some paradigm shift is needed for thinking about the directions of future developments that will show societal benefits also open up private-sector opportunities. In this context, we develop a multi-agent advanced traffic management and information systems (ATMIS) framework with day-to-day dynamics where private agencies are included as traffic information service providers (ISPs) together with public agencies handling the traffic control and the users (drivers) as the decision-makers. One important paradigm shift is that the emergence of private ISPs makes it possible to obtain path-based data via retrieval of individual trajectory diaries and current position information from their subscribers. The availability of such path-based data can bring about the development of new path-based ATMIS algorithms. Such new algorithms can be capable of taking into account the routing effects of advanced traveler information systems (ATIS). Under the assumption that the traffic management center (TMC) has some (even approximate) knowledge of the ISPs’ optimal strategies, it is possible to design optimal route guidance and control strategies (ORGCS) that takes into account the anticipated ISP reactions in terms of route-level flows. In light of these issues, we develop a routing-based real-time cycle-free network-wide signal control scheme (R2CFNet) that uses path-based data. The scheme also allows the avoidance of day-to-day games between ISPs and signal control through the use of weights on the queue delays in the control objective function. The weights are essentially operator parameters designed to incorporate ORGCS and day-to-day behavior. The proposed control scheme, of course, responds to detected traffic (demand) rates on a real-time basis in response to the control delays on network routes. Another theoretical advance in the research is in the development of a modeling scheme that uses a new optimization algorithm for a convergent simulation-based dynamic traffic assignment (DTA) model. This model incorporates a Gradient Projection (GP) algorithm, as opposed to the traditionally-used Method of Successive Averages (MSA), and it displays significantly better convergence characteristics. A consistent day-to-day dynamic framework is also developed, incorporating an elaborate microscopic simulation model to capture traffic network performance, to study network dynamics under multiple private ISPs and the new signal control scheme. The results of parametric simulations have shown that the proposed framework is capable of effectively capturing the effects of the interplay of urban traffic route guidance, network control and user response. It is seen that an appropriate combination of ATIS market penetration rate and the special-purpose signal control settings could divert some portion of travel demand to different routes. This is achieved by constraining the signal settings to conform to certain longer-term strategies. The performance and efficiency of the components of the proposed framework such as the DTA model, the day-to-day dynamics model and the R2CFNet control scheme have been investigated through various numerical experiments that show promising results. Lastly, several future topics of relevance to the framework are discussed.