If you haven't yet been on the Chester Valley Trail from Frazer to King of Prussia, PA you are missing one of the nicest trail systems in the Delaware Valley.
On August 11, 2014 I started my ride at the Church Farm area parking lot and rode 12.5 miles east to the trail's end just past the Schuylkill Expressway.
The parking lot is large enough but is going to be expanded shortly and there are restrooms and picnic tables nearby.

Here are three photos of how the trail crosses over the Expressway.
I can't say it's the most scenic trail since I rarely take photos along the way, but it's a fun and safe way to bicycle (or walk) through the "Great Valley" from Frazer to east of King of Prussia.

Eventually, it will connect with the Schuylkill River Trail and to the trails in Valley Forge National Park.
Also, a short extension on the western end from the Exton Walmart to the Church Farm area is due to open in the near future.
Apparently, they are waiting for the crossing lights to be installed at Route 30 in Exton.

In the end, you would be able to bicycle from Exton into Philadelphia by bicycle along this safe and mostly flat trail system!
There are a number of highway and road crossings, but they are marked clearly with Stop signs, gates, bollards and crossing signal buttons to push to safely warn traffic of your presence.

So get out and enjoy this great trail, especially with the cooler fall days coming.
Really, today was very comfortable riding the trail since much of it is tree-lined and shaded.
Get out and ride!