It's amazing how far off from level one may look. I worked with an old timer who ran a dozer with just a pocket eye level and that man could hold a grade unbelievably well with it. We were finish grading 3/4" stone in a huge cellar hole for the footings and he had it well within .1 foot.
Near here is the kettle moraine forest, with 100s of miles of trails (glacial till, highly erodible). Originally they were horse and or buggy/wagon trails that went anywhere that was logical - straight up hills and following ridges etc. Later they were used for outdoor types, like snowmobiles, hikers etc. It was the mtb bikes that changed the mindset around - since they could really rip up the ground, but couldn't really tolerate 10ft deep gulleys (hardly). They tried all kinds of erosion control measures - plastic mat, rubber razor deflectors, treated steps, hardpack limestone, all to no avail. In the end, all of that has been removed, and trails rerouted to trend along the slope not against, and surfaces now with reverse camber to keep water from gaining volume and speed. Just saying - I see forest roads cut in for housing or other access straight up hills, and think - when they've had enough maybe they'll fill in the canyon created and do different. One neighbor started that way, and ended up dumping motor oil and fist sized stone the whole way and is still fighting it all 40yrs later.
