The Continental Divide Trail from Bannack Pass to CDT - Elk Mountain
is a doubletrack that follow the divide itself.
It can be steep, both up and down, so there will be hike-a-bike sections.
Look for the old railroad tunnel near the western end of this CDT section. It is blasted closed on the Montana side but still open on the Idaho side.
Use this trail to access CDT - Elk Mountain
as a shuttle from Bannack Pass to Idaho's Hawley Creek. Or a loop with the addition of the Hawley and Railroad Canyon roads.