Library Systems have been developed so that the users can borrow or return books to any libraries. In the planning process of public libraries, we have to discuss the effectiveness of Library Systems. In this paper we construct a model which describes library-choice behavior of users, and propose a method for measuring the travel cost to libraries. Our model is based on a logit model whose utility function consists of facilities' attractions and travel cost in the term of utility. Through the mathematical consideration, it is shown that the travel cost can be measured by using the data of library-choice behavior of users. The numerical examples on Yokohama-City Libraries show that the travel cost increases according to not only the distance to libraries but also the geographical features around.
