I biked the West River Trail the other day in southern Vermont, It is basically an old railroad bed that went from Brattleboro to Londonderry Vermont along the West River. It is broken up now into several sections and I have done two so far. The first section starts in Brattleboro and goes up to the old covered bridge on Rt 30. This section round trip is about 10 miles and hugs the West river tightly with lots of great views. The trail is a combination of single track, gravel dirt road and sparsely used tar roads. If you look closely there is an old granite quarry that is quite spectacular about midway though the trail.
The next section of the trail did was also about ten miles and goes from South Londonderry down river along the West into the Winhall Campground. Again the trail is a mix of single track and well maintained dirt roads and uses a significant section of the campgrounds roads for its path. Eventually the trail dead ends into an steep uphill trail that is more suitable for hiking than biking. This part of the West trail continues to the backside of the Ball Mountain.
The parts of the West River trail I rode are not suitable for road bikes but hybrids or other wide tired bike would be fine.
Here is a link to the West River Trails website