This paper presents the implementation of providing traffic information using the Road-On Map in order to accomplish rapid and reliable traffic management in the southern area of Kumamoto Prefecture following the heavy rainfall disaster in July 2020. ETC2.0 probe data collected from vehicles equipped with ETC2.0-compatible on-board units are used by Road-On Map to determine whether or not roads are passable. It has been difficult to rapidly and efficiently provide traffic information using real-time data until now, however, by using ETC2.0 probe data, it is now possible.