In many countries, several mitigation techniques are in use to minimize road-kill, habitat loss, and reduced habitat quality. In Japan, the significance of mitigation techniques is currently uncertain, and no standard procedures are being used to minimize the detrimental effects that road systems can have on wild mammals. Therefore, we studied the ecological effects of road-crossing structures(RCSs) in this country. We analyzed the biological and physical factors that contribute to the selection of RCSs by wild mammals. Furthermore, the future direction of mitigation techniques and the placement criteria in Japan is discussed.

First, we investigated the availability of various RCSs (box culvert, pipe culvert, underpass, overpass, eco-bridge, drift fence, planting, other) for focal species of conservation on 86 roads (13 roads in Hokkaido, 30 roads in East Japan, 34 roads in West Japan, and 9 roads in Okinawa and Tsushima). Second, we selected 2 roads (Higashifuji-Goko Road and Toyotomi Bypass) from these 86 and set up infrared sensor cameras to investigate RCS use by species of wild mammals. We suggested the placement criteria for RCSs based on the result of camera traps for wild mammals survey.