Sangho Choo

Relationships between US consumer expenditures on communications and transportation using almost ideal demand system modeling: 1984-2002

Abstract This study analyzes aggregate consumer expenditure data from the US between 1984 and 2002, to determine relationships between expenditures on transportation and communications. We first identified 15 categories of goods – nine for transportation, five for communications, and one for all others – and obtained prices for each category across time. Then, we applied the linear approximate almost ideal demand system (AIDS) method for estimating consumer demand functions, aggregating the categories to six (non-personal vehicle (PV), PV capital, PV operation, electronic communications media, print communications media, and all others) due to the small sample size. The results indicate that transportation and communications categories have both substitution and complementarity relationships. The existence of effects in both directions (substitution and complementarity) is testimony to the complexity of the relationships involved, with both generation and replacement possible and happening simultaneously. In addition, expenditures in the transportation categories are generally more income-elastic and price-elastic than those in communications, indicating that communications expenditures are more essential than those for travel. The transportation categories have both substitution and complementarity relationships with each other, while the two communications categories have a substitution relationship.

Geographic Distribution of E-Shopping

The proliferation of Internet shopping has imposed enormous pressure on traditional stores. Few studies have examined the geographic distribution of online buyers and its implications on retail development and transportation. Using 585 Internet users in the Minneapolis and Saint Paul, Minnesota, metropolitan area, this study develops structural equation models to test two competing hypotheses regarding the connections between spatial attributes and e-shopping: diffusion of innovation and efficiency. The results demonstrate that the influence of shopping accessibility on e-shopping is not uniform and depends on the locations in metropolitan areas. Specifically, Internet users living in urban areas, areas with greater shopping accessibility, or both tend to purchase online more often than their counterparts in other areas because the former are better educated and use the Internet more than the latter. However, low shopping accessibility in exurban areas does promote the use of e-shopping as compared with exurban areas with relatively high shopping accessibility.

A freight network planning model in oligopolistic shipping markets

The paper presents a multi-level hierarchical approach which models the oligopolistic behavior of carriers in maritime freight transportation networks. With the merger of the carriers’ industry and some dominant carriers in today’s shipping markets, carrier competition frequently exhibits an oligopolistic nature. This study considers the following three types of carriers; ocean carriers, land carriers, and port terminal operators. The oligopolistic ocean carriers, land carriers, and port terminal operators compete with each other in their pricing and routing decisions. The carriers determine service charges and delivery routes at different parts of the multi-modal freight network, creating hierarchical relationships. When using a game theoretic approach, ocean carriers become the leaders in an oligopoly shipping market. When dealing with individual carrier problems, the Nash equilibrium reveals the optimal decision where each carrier obtains the greatest profit. A three-level model is formulated to capture the interactions among different types of carriers. The validity and capability of the model gets demonstrated through an empirical example.

The Effects of the Emission Cost on Route Choices of International Container Ships

Maritime freight shipping has increased significantly and air pollution from international ships has grown accordingly, having serious environmental effects all over the world. This paper analyzes the effects of the emission cost on ocean route choices, focusing on international container ships. First, the paper formulates a freight network model that captures decisions and interactions of ocean carriers and port terminal operators in the maritime freight transport system. Then, the emission cost is calculated based on an activity-based approach as a component of the ocean transportation cost function. A case study is examined to find if the emission cost affects ocean route choices. The results indicate that the optimal ocean route and transportation cost are changed distinctively due to the emission cost. The research discusses how the emission cost plays a role in route changes and why ocean carriers have to consider these costs in their routing decisions.

Identifying differences of travel time budgets between the elderly and the nonelderly groups using PSL structural equation models: A case study for Seoul metropolitan area

ABSTRACT To date, aging is one of the most important issues in our society because of its significant socioeconomic impacts. Corresponding concerns about the transportation needs of the elderly have led to a focus on the mobility and quality of life of the elderly and motivated various studies of senior mobility. As the fastest aging country in the world, Korea will need to provide insightful information for an aging society. The purpose of this study is to investigate the difference in travel behavior between the elderly and the nonelderly groups by focusing on travel time budget (TTB), using the 2006 household travel diary survey data from the Seoul metropolitan area. We develop partial least square (PLS) structural equation models to identify major variables that affect the TTB of each of the two groups and then compare the differences between the models. Model results indicate that the significant explanatory variables differ between the two age groups, and the degree to which the variables affect the TTB differs by personal and household characteristics.