This paper presents a qualitative study of several old ridge roads and also presents the examples of safety measures by utilizing the old ridge roads during such disasters as heavy rains and earthquakes. Since the old ridge roads can be used for the people coming and going during the blockade period of the modern riverside road due to disasters, some of old ridge roads can be named, therefore, as the fail-safe paths.
This paper is written about old ridge roads, based on the examination of references and the field reconnaissance without any technical data, mainly focusing on the central Japan, the key map of which is shown in Fig.1. Many mountainous medieval roads in the central Japan area are located along the crest of mountain ridge. Such old ridge roads have the distinguish history, which can be proved by the existence of old temple, old shrine, Goddess stone, old traveler's guardian deity, statue of Mercy, etc. Also, the old ridge roads have been steadily existed for a long period after the experiences of historical disasters. Furthermore, some old ridge roads have been utilized as the fail-safe path during disasters, which is proved by the experiences of the recent disasters such as heavy rains and earthquakes. OLD RIDGE ROADS The ridge road had been dominant in the mountainous area of Tokai region since the Japanese Warring State Period (1467–1568) or before. When it arrived at the pacific Edo period (1603–1867), the road alignment had been selected from ridge road to riverside road. However, the alignment of modern highways in the mountainous area seems to return to the alignment of old ridge roads. The profile of modern highways in the mountainous region is designed with gentle slope and applied the shortest way by using bridges and tunnels (Takebe, 1992).
