Makoto Okumura and Hiromichi Yamaguchi
The service level of inter-regional transportation on all but the busiest arteries in Japan will decrease due to the declining population. Currently, only business and sightseeing travel are considered as major drivers of inter-regional traffic flow for the planning of transportation network improvements. But private travel for visiting remote family is also essential. The social importance of this type of travel will increase with the future aging population, when many people who had made inter-regional migration will need to take care of their elderly parents living in their region of birth. In this chapter, this type of inter-regional travel is analysed using the zero-inflated Poisson models. The authors conclude that both the birthplace distribution and the service level of transportation affect the frequency of these trips. In other words, travel to visit elderly parents acts as an integrator of historical inter-regional migrations.