Chun Wing Yip

Modeling transfer and non-linear fare structure in multi-modal network

In metropolitan areas where multi-modal trips are common, modeling transfers is an important issue. The existing approach of connecting multi-modal networks, without attending to the number or kinds of transfers, cannot fully describe actual behavior. In addition, the common practice of non-linear transit fare structures imposes certain modeling difficulties on the assignment approach. In this study, we develop a formulation to overcome these two difficulties, namely the number and kinds of transfers are explicitly considered and non-linear fare structures accommodated. Through a state augmentation technique, we transform a multi-modal network to one we call state-augmented multi-modal (SAM) network. Once formulated, the SAM network behaves like a simple network and can be combined with traffic assignment or network analysis procedures. A numerical example is provided to illustrate this approach.

MULTIMODAL TRANSIT SERVICES WITH HETEROGENEOUS TRAVELERS

Public transit systems play a pivotal role in serving the transportation needs of many major cities. In Hong Kong, for example, more than 90% of the 11 million daily trips are provided by public transit services. The planning and design of these services, therefore, are important welfare considerations. The situation is particularly intriguing if these services are to be provided by the private sector whose primary objective is not to ensure welfare gains or an efficient utilization of the road space but to maximize profit. Analyses are of significant interest and potential application to many transit-oriented cities. In metropolitan areas in which multi- or intermodal trips are common, modeling the multimodal route-choice characteristics of heterogeneous travelers and the strategic interactions among the many private firms are important issues. In this study, mode-choice models were integrated in a network of competing transit operators. A novel network structure, designated as the state-augmented multimodal (SAM) network, was developed via a state augmentation approach. With this SAM network, the effect of fare competition and regulations on social welfare as well as on profitability of the companies could be examined. A case study of the ground transportation system connecting the Hong Kong International Airport with the city’s downtown was conducted.

Transit Services in a Competitive Market

Since the new Hong Kong International Airport debuted on July 6, 1998, ground trips to the airport have undergone drastic changes. A number of transit modes are provided to connect the new airport with the territory, including three major ones—Airport Express Line (AEL), Air Bus (A-bus), and External Bus (E-bus). All of these transit services are operated by profit-driven businesses, dividing the 167,000 daily trips. Currently, the Hong Kong government imposes fare control on the bus services, whereas the rail service (e.g., AEL) is exempt from such control. The fare changes resulting from this competition were examined to assess their impacts on the traveling public as well as on each operator. In addition, an evaluation was made of the impact of deregulating this policy of fare control and allowing the operators to compete freely in a noncooperative manner. Transit services in a competitive market could lead to very different outcomes. For some districts, a transit operator could increase revenue by fare increases, whereas for other districts, revenue increase could be achieved only with fare reduction. Where and why competition falls into these different operating paradigms is an interesting topic for investigation. The methodology for this analysis, as well as the results based on actual data, is discussed.