Special Roads for Colorado
Colorado does not use the dirt road type unless it is for "2 track" unimproved roads. Any road that a highway vehicle could easily travel would not be considered a "Dirt Road/4x4 trail." See this Forest Service Roads section about Forest Service roads for some clarification.
If the road has been improved at all (meaning that it is a gravel road), we use the street road type. There may be special circumstances, so contact an Area Manager with any questions.