Abstract
The objective of the present study is to find solutions for transportation problems using a theoretical framework related to social dilemmas. The present study proposes a definition of social dilemmas specific to infrastructure planning, and discusses how strategies for solving social dilemmas, which have been investigated empirically and theoretically in sociology and social psychology, can be applied in transportation planning. This study indicates that what is seriously required for solving transportation planning is not only TDM or TCM but also policies to activate public spirits of transportation system's users, and that practical and scientific researches to understand how we can activate the pubic spirits, are essential for transportation planning.
