Forest Service Roads
Among many of the functions of the United States Forest Service (USFS) is the development and maintenance of Forest System roads that are relied upon by USFS and the public. The USFS uses these to maintain its forests, aid in fighting forest fires, allow public use, and other functions.
Some of these roads are critical to local populations not just for recreation, but for regular travel. Such use is likely more common in rural and western states than it is for urban or eastern states.
Waze and Forest Service Roads
One key resource are the USFS Motor Vehicle Use Maps (MVUM) that identify specifically where USFS allows use of their roads by public motor vehicles.