The ideal form of transdisciplinary research as seen from the perspective of sustainability science, considering the future development of IATSS

• The aims of sustainability science are fundamentally the same as those of IATSS.
• A transdisciplinary approach builds a common direction focused on solving problems.
• IATSS needs a transdisciplinary approach engaging a wide community of stakeholders.
• Scientific knowledge must be combined with traditional and local knowledge.
• IATSS should develop participation in events and links with existing networks.

Sustainability science aims to solve pressing global challenges by integrating the natural sciences with the social sciences and the humanities. This also reflects the aims of IATSS. An interdisciplinary approach removes barriers, but a transdisciplinary approach additionally seeks to create a new, unified direction with a focus on solving problems, engaging a broad range of stakeholders outside academia. IATSS has been successful in removing barriers between specializations, but it must consider shifting from the interdisciplinary toward the transdisciplinary, and how to connect with a wider community of stakeholders.Scientific knowledge must be combined with other knowledge systems such as traditional and local knowledge, leading to a more effective interface between science, policy and society. Advanced methods and technology must be tailored to reflect local conditions and values—each transportation society is supported not only by technology and institutions but also by culture and patterns of behavior.Population decline and aging are among the greatest challenges facing Japan, and addressing them in the context of a transportation society will be an important issue on the agenda of IATSS. It will be critical not only to look at the physical, economic and social issues, but also to focus on people themselves. In Japan the development of renewable energy has accelerated since the Fukushima nuclear accident, but it needs to be linked to the broader rebuilding of resilient local communities. For IATSS the challenge is to consider transportation frameworks suitable for such compact cities and rural communities.Considering the future development of IATSS, I suggest promoting strategic participation at related international events, and building institutional links with existing networks. Rather than serving as a specialist journal, IATSS Research should look at traffic safety in a broad sense, and discuss visions for transportation societies as well as concrete research findings.