From the 80's, shop-around behavior model (SABM) has been developing to evaluate the location pattern of shops and size of it within the City Center Retail Environment (CCRE). Various types of model, based on the SABM were developed such as forecasting the number of shoppers and their expenditure for each shopping sites and CCRE. Also the transportation mode within the CCRE has been evaluated with money term by using SABM, such as one coin bus in Fukuoka. Moreover the Poisson regression model with choice based sampling data was enabling to predict the number of visitors to CCRE. This paper is conceptualizing the Specialization Coefficient (RC) by shop-around behavior and testing in Kamata District in Tokyo Metropolitan Area, Japan. To specify, the RC is the indicator between each transportation mode and consumer shop-around behavior, which was defined by the shop-around effect (RE) and disaggregate typed RE for each transportation mode. From the result, visitors by bus, private rail company (Tokyu Line) and bicycle highly effecting Kamata district (RC is greater than 1). On the other hand, visitors by walk, other rail companies (JR and Keikyu Line), taxi, personal car and motorcycle have less effect (RC is less than 1). According to the result, RC is the useful indicator to assess the transportation mode within the CCRE.