Solid roads should be improved roads that are typically public roads. A paved or gravel road that is maintained by the State or County will be public. FS, I'm assuming is "Forest Service" road will be public. Trespassing typically occurs when people are driving on two-track roads. A two-track road on a map will look like this = = = = = = = . So if you are on a two-track driving on BLM (yellow on the map) and it crosses private land (white on the map), you will be tresspasing if you continue to drive.