What Is A VT Class 4 Road Anyway?
A Class 4 road as defined by the State of Vermont is a road that is not Class 1 (State highways),2 (Important town highways) or 3 (Traveled town highways). Road classes 1,2 and 3 are required to be maintained by the town (or state) to be 'negotiable under normal conditions all seasons of the year by a standard manufactured pleasure car.'
Therefore, we can assume that Class 4 roads are not maintained, and are therefore of questionable condition. (vermontroads.net)
The NH equivalent are Class VI roads:
What Is A NH Class 6 Road Anyway?
Class VI roads are “all other existing public ways,” meaning public ways not otherwise classified as Class IV or Class V roads. Class VI roads include those that have been discontinued subject to gates and bars, as well as those that have “not been maintained and repaired by the town in suitable condition for travel” for five successive years or more.
Therefore, we can assume that Class 6 roads are not maintained, and are therefore of questionable condition. (nhroads.com)
Many club gravel rides and "adventure rides" will include some Class 4/Class VI sections. These can range from seasonal dirt roads (not much different from maintained dirt roads) to long-abandoned farm tracks and logging roads. Conditions can range from easy riding to challenging riding to hike-a bike.
Some riders enjoy this kind of terrain. Some hate it. Most gravel riders seem to fall somewhere in between, where a small amount is fun but too much gets frustrating.
From a post by Peter Burghardt to the Upper Valley Velo mailing list.