Generally speaking, the opening of an expressway affects the economy of adjacent areas in a postive manner, as travelling time is reduced and other conditions necessary for conducting business in such areas are improved. For example, an expressway could improve the efficiency of farm produce transport, increase the number of local manufacturing plants, and encourage tourism. However, improved traffic conditions reduce the distance between municipalities and could negatively affect the local economy by enabling businesses and therefore consumers to leave the area. This possibility can be a particular concern depending on population size and site conditions for manufacturers and distributors. The time required for travel between various municipalities is shortened by the opening of an expressway. An expressway changes retailers relative site conditions and thus affects consumer actions. The effects of an expressway on retailers normally take the form of an outflow of consumers from less attractive to more attractive areas, particularly from outlying municipalities to a more centralized area. Therefore, for retailers located in outlying municipalities, the opening of an expressway could lead to an outflow of consumers who had previously shopped closer to the more attractive core community. In this paper, I have analyzed how these factors affect competition among retailers in neighboring municipalities. My analysis was based on research comparing broad-based consumer actions before and after the opening of an expressway. A probability model involving the selection of purchasing sites by consumers was used in the analysis. Based on the findings of this research, I derived spatial patterns for consumer movement from outlying municipalities to the core community following the opening of an expressway. I attempted to reveal how the effects of a newlyopened expressway differ depending on the types of items purchased and conditions for competition among retailers in neighboring municipalities.