See
http://localhost/mb/topic/turtle-creek-rail-trail/ and the Turtle Creek Trail website @
http://www.murrysvilletrails.org/tc.htm
From Trafford I sometimes take the 5th Street Bridge (on the west end of Trafford, over Turtle Creek and ball fields) which turns into Broadway, then turn left on Mosside and go over the bridge (also over Turtle Creek) and turn right onto Wall Ave. Then come up to the Patton Street bridge (north of where Wall Ave merges into Station Street) and go over the Patton Street Bridge (again over Turtle Creek) and turn left onto Airbrake Avenue (note that Airbrake Ave. is one-way in the other direction here, though), optionally taking the small asphalt trail (which is on the left, down in the grass area, right after Turtle Creek turns to be a bit further from the road) which rejoins Airbrake after a little bit (by the playground). Then Airbrake becomes Penn Ave. by the Greensburg Pike/Monroeville Ave./Thompson Street area; continue on Penn, which soon becomes Braddock Ave. Soon after, Braddock becomes Tri-Boro Expressway; take this until it turns back into Braddock Ave. (Tri Boro Expwy is a higher-speed, highway-like road, but is two lanes per direction and usually low traffic, so easier to ride on). Continue past the steel mill and then through the small town of Braddock, until the Rankin Bridge. The easiest way from here is probably to go over the Monongahela River on the Rankin Bridge, and at the end of the bridge either turn left, and ride on the left sidewalk then shoulder (the river side of the road) for a short time until right after the road which goes under the bridge merges in, and then you will see on your left a little driveway-type road, which takes you through a little trail/old-road to the GAP right by the Whitaker Bridge (see
here; via @paulheckbert at
http://localhost/mb/topic/rankin-bridge-bike-lanes/#post-317041).
