Its been a while since it was posted but I am new to road biking in clarksville. Have a look here
http://www.clarksvillecentury.com/ this is the website for the clarksville sunrise century and it has the 30, 60 and 100 mile routes used. If you look around the kenwood church you will find a nice quiet (and marked with arrows route. the following link is a route we did (approx 9.5 miles and while there we encountered other cyclists. It is quiet and very little traffic (on the sunday we did it). using the webpage provided you can map more routes in the area out and know how far you will do.
http://www.gmap-pedometer.com/?r=2650258
Hope it helps
Steve