Classification of Unrealized Trips and Identification of Mobility Difficulties: Urban–Rural Differences in Japan

For various reasons, individuals sometimes cannot go on trips. These are known as unrealized trips. In this study, we focus on discretionary trips, such as those for shopping and leisure, and analyze the factors that lead to their lack of realization due to insufficient mobility and transportation services. Based on survey data collected in Japan from populations of various sizes, K-prototypes clustering was conducted, and respondents were classified into three groups: those who only travel by private car, those with multiple transportation options, and transportation-disadvantaged individuals. Notably, the transportation-disadvantaged group exhibited a higher frequency of unrealized trips and was present in both urban and rural areas. Estimation results of the zero-inflated bivariate ordered probit (ZIBOP) model revealed that younger and lower-income individuals were more likely to experience unrealized trips. Moreover, railway frequency and last service time of bus were significant factors in urban areas, while bus service levels played a key role in rural areas. These findings suggest that “transportation-disadvantaged” individuals should be defined not only as those without a car or driver’s license but also as those who lack alternative mobility options.