Connecticut River Scenic Drive is a 41 mile trail located near Hanover, NH. The trail is primarily used for scenic driving and is accessible year-round.
It is a very beautiful drive but much too much traffic. The river, the mountains, the forrests and some of the quaint areas make it a beautiful trip.
I have traveled this route a number of times over 50 years. Despite how busy the road is in any drivable season, it is a classic for scenery of mountains, forest, river, etc. It is spectacular in the fall, when it is incredibly busy. Somehow, word about New England foliage leaked out. In a good year, it is better than you've heard. In a bad year, it still beats almost anyplace else.