Wolf, mountain lion, and black bear use underpasses in the Rocky Mountains of Alberta and the Cascades. Different types on faunal overpasses have been built and all are successful. Width from the animal's perspective apparently is the most important variable. Thus over passes in France, Germany, and Holland that are up to ca. 50 m wide at the beginning and end, but which narrow to 8-35 m in the center are somewhat successful.
Some animals appear frightened in entering the narrows.
More successful are overpasses of 50-80 m width in Holland and Germany. These structures are double-vaulted, except for one 80 m wide Dutch overpass on pillars that is flat beneath. Two double-vaulted overpasses of ca. 50 m width for wolves, bears, and elk, are planned for construction near Calgary, Canada. Landscape connectors are structures that permit the crossing of all natural movements and flows across a road or rail corridor.