conference paper
working paper
Using data from a 2001 survey of managers of 700 trucking companies operating in California, we tested competing hypotheses about the relationship between managers’ perceptions of the impact of traffic congestion on their operations and their companies’ adoption of routing and scheduling software. Demand for automated routing and scheduling was found to be influenced directly by the need to re-route drivers, and indirectly by the need, generated by customers’ schedules, to operate during congested periods. We were also able to identify which types of trucking companies are most affected by congestion and which types are more likely to adopt such software.
working paper
Modern travel-behavior surveys have become quite complex; they frequently include multiple telephone contacts, travel diaries, and customized stated preference experiments. The complexity and length of these surveys lead to pervasive problems with missing data and non-random response biases. Panel surveys, which are becoming common in transportation research, also suffer from non-random attrition biases. This paper shows how Rubin’s (1987a) multiple imputation methodology provides a unified approach to alleviating these problems. Before discussing solutions to problems caused by missing data and selection, it is important to recognize that their presence causes fundamental problems with identifying models and even “simple” population estimates. Section 2 reviews this work and stresses the need to make generally untestable assumptions in order to carry out any inference with missing data.
working paper
Understanding the process of activity scheduling is a critical prerequisite to an understanding changes in travel behavior. To examine this process, a web-based activity survey program, REACT!, was developed to collect household activity scheduling data. REACT! is unique in that it records the evolution of activity schedules from intentions to final outcomes for a multi-day period. This paper summarizes an investigation of the structure of activity/travel patterns based on a REACT! data set from a pilot study conducted in Irvine, California. The term structure refers to the outcome of a set of decisions facing individuals as they conduct their daily activities. At a minimum, structure can be interpreted as the sequence by which various activities enter one’s daily activity scheduling process. Results of the empirical analyses show that activities of shorter duration were more likely to be opportunistically inserted in a schedule already anchored by longer duration counterparts. Additionally, analysis of tour structure reveals that many trip-chains were formed opportunistically. Travel time required to reach an activity was also positively related to the scheduling horizon for the activity, with more distant stops being planned earlier than closer locations.
conference paper
published journal article
book/book chapter
Housing plays a central role in urbanization and urban sustainability in the United States. Population growth in and migration to urbanized areas is accompanied by demand for housing. The response to this demand, housing development, in turn consumes increasingly more land, spurring urbanization and fostering sprawling development patterns. With over fifty years of growth, mass housing production, and a cultural propensity for consumptive behavior, the United States serves as an exemplary case through which to examine urbanization and the featured role of housing within this larger process. This case also reveals the effects of decisions by housing producers, consumers, and
Phd Dissertation
This dissertation contains two standalone essays in which urban location models are developed to analyze various issues in urban and transportation economics related to commuting distances, location patterns, and urban sprawl. The first essay examines possible reasons for ‘wasteful’ or ‘excess’ commuting, whereby observed commuting distances generally exceed those predicted by standard models of household location choice. It is likely that households are willing to accept a longer commute to work if proximity to certain amenities is important to them. To examine this issue, a model with two job centers, a central business district (CBD) and a subcenter, is developed. Households are assumed to either have preferences for amenities (which are located in the CBD), or they do not, regardless of job location. It is shown that households who work in the subcenter but who like the amenities in the CBD may be willing to locate further from their jobs in order to be closer to the amenities (thus increasing average commuting distance in the city), especially when proximity to the amenities is highly valued. The second essay focuses on urban sprawl and the effects of different anti-sprawl policies on welfare and urban structure. A model with heterogeneous households and firms that can locate anywhere in the city is developed. The main features of the model are traffic congestion and household preferences for open space, both of which are closely associated with urban sprawl. The model also includes agglomeration economies, providing a more complete picture of how firms choose locations. Numerical results show equilibrium location patterns, rents, and wages under different model specifications. The model is then used to analyze the impacts of two popular anti-sprawl policies: congestion tolling and an urban growth boundary. The results suggest that congestion tolls may decrease welfare if unsubsidized agglomeration economies are very high, because higher travel costs lead to the decentralization of firms. Meanwhile, the urban growth boundary increases the amount of open space but reduces the supply of land for residences and offices, and is welfare-improving only if household preferences for open space are very strong.
MS Thesis
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.
published journal article
Rent extraction by public sector workers may be limited by the ability of taxpayers to vote with their feet. But rent extraction may be higher in regions where high amenities mute the migration response. This paper develops a theoretical model that predicts such a link between public sector wage differentials and local amenities, and the predictions are tested by analyzing variation in these differentials and amenities across states. Public sector wage differentials are, in fact, larger in the presence of high amenities, with the effect stronger for unionized public sector workers, whose political power may allow greater scope for rent extraction.