The Uncompahgre River Trail is planned as a 37 mile trail from Ouray to Delta, but only the Ridgeway and Montrose segments are currently completed. This short 4.5 mile segment is called the Ridgeway Greenway and parallels 550 north to the Ridgeway Reservoir which is in the Ridgeway State Park.
Here's a trail sign along the way (click to enlarge.) It is hard to read but gives an idea of the trail's route. Once you get on the trail, it is easy to follow.
You begin with a few blocks of the town and a few road crossings, and after going over this old railroad trestle (photo below) crossing the Uncompahgre River, you'll be in open country, mainly sagebrush and river with a tiny bit of the trail running right alongside Highway 550.
You are rewarded with some lovely scenery such as the photo below. At the 1 mile mark is a small park on your left with a washroom and other amenities.
Though most of the trail is pretty level, about midway to the reservoir you do have a hill that will get your heart and lungs working a bit. It's okay to walk the bike if need be -- we call it cross-training! As you descend the other side, you run alongside the highway and pass through a gate in the tall wildlife control fence. The sign tells you during which months the gate is to be closed behind you (winter months.)
The trail segment ends at Ridgeway State Park which has about four different parking lots. Of course, you can park here and bike south if you prefer not driving all the way into Ridgeway. Washrooms are also available in these state park lots as well as beautiful views as seen below.
The trail segment will only provide a ride of about 8.5 miles, but you can always turn around and do it again, or drive the 26 miles to Montrose and bike their segment of this trail.