I've logged about 20k miles of road biking across the United States namely in WA, MO, OH, PA, MD and FL, and maybe 10% of that on trails. To get to stay 99% of the time on a car-free trail for almost 50 miles (as a loop) is rare- and to have some scenery- is nearly unheard of. Thrilled to be in CT now and using this as my go-to ride.

We rode this trail on 9/12/20, starting at the parking lot on route 63.
Overall, a nice trail, but it has a lot of plusses but also some things that could be considered “minuses” by some.
Plus:
Shaded, pretty sections high over the adjoining forest.
Some nice scenery including horse farms (and horses share the trail, we passed several), plus several ponds. Route goes through the woods the whole way…very little in the way of passes through suburbia.
Not crowded.
Not a huge number of road crossings, and typically with good sight lines.
No big hills, some gradual ups and downs.
Minuses:
Most of the train is hard packed dirt or stone dust that makes for a good surface. However, there are significant sections that are a bit rougher. Some of the road crossings involve a downhill, cross the road, and then an uphill…often with a lot of stone or sand involved. There is a section around mile 8-9(when going West) where the trail follows something like a creek bed, with large stones that make it problematic (we walked this section). There are some embedded stones along the way so you have to watch where you’re going and steer around them..or even walk briefly. Some sections do have some drainage issues, so just need to be careful there. And parts of the trail become more like singletrack. We were able to navigate the entire route with our mountain/trail bikes (30 or 32 cc tires)…I would not recommend a conventional skinny tire road bike here.
Please don’t think the minuses outnumber the plusses here. Overall I recommend this trail because it’s pretty and ridable. Maps are available at the Connecticut DEP website.
Finally I recommend starting at the Naugatuck route 63 parking area…several other posters have noted that there’s basically no parking if you start in Southbury.
Check out the Air Line trail and the Hop River trail, not too far away in central Connecticut, for other options you may want to try.

Heading south toward the Colchester spur, the map shows a fork in the path that veers off to the left. This doesn’t exit. You have to continue down an take a real left. There’s a sign.

Beautiful views of the river. Asphalt walk/bike way. Ranger on duty at Great River Park boat launch/parking area.

End to end and back is a nice walk pick a time later in the day less people. Flat good starting walk for beginners before taking on trails. Year round good walk

Took the family and it was very clean and an excellent time. Windy and lots of hills and downhill runs. Recommended

This was a lovely, but popular walk. The only issue is that all but one small car park has been closed to non-local residents due to COVID. So unless you have a parking permit, you’ll need to head to Palace Street where there are a small number of metered parking spaces.

Rode east to west from Bolton to Hartford and returned. Trail in good shape on eastern end but less utilized and deteriorating somewhat in some parts of Manchester and East Hartford. Trail has a good assortment of hills. Some minor stretches are on town roads and there is a mile long section in East Hartford where you can cut through the former Pratt & Whitney complex to hook up with the trail again where you cross the CT River via the Founder's Bridge and enter Hartford. The sites in Bushnell Park are always a treat to round out your ride! Some parts of the Greenway lead one to question which way to continue so have your TrailLink map handy and look for signs! A rewarding ride and gradual uphill climb on the return to the car near Exit 5 off CT Rte 384. Approx. 38 miles.

First & most important: start in Naugatuck !! Zero parking in Southbury. Don’t be put off off super steep hill - it’s only about 80 yards - just wheel your bike up to the top & you’ll be on nice flat rail bed. First time ride this trail. Had a raw unfinished feel to it. Some steep up & downs at road crossings which were little off putting outbound but on return was expecting them & didn’t even have to dismount for 3 out of 4 of them. One section like riding a dry river bed - take it slow or walk - only 200 yards or so. Sone areas muddy and would be messy after rain. Despite unfinished feel was well maintained and even huge fallen trees had been cleared. Very peaceful ride. I have hybrid bike regular tyres not fat ones.