Pittsburgh 5th Ave Bridge

I'm confused with the amt of rails throughout Pittsburgh. At 5th ave does the Keystone Sub branch along the river? Is traffic heavy in Pittsburgh?

Got Google Earth? Hours of fun and you can find all the lines.
I only lived in Pgh. for a year or so a long time ago (1989), no idea how traffic is these days.
I was a teenager at the time, who was not yet reformed on the issue of trespassing. I spent a lot of time walking the tracks around there, something I no longer recommend.
I lived right off 5th Ave above the Boundry St. tunnel. Not sure if that is the Keystone. But one day I dropped down on the north side of the tunnel entrance (by the east busway) and walked the line west/north. It rejoined a main behind the Iron City brewery, then branched again. The main turned into a small yard; the branch curved north and went over the Allegheny River on a trestle. I walked to the town of Etna and back.
Again, I have no recent info to offer, just these memories.

It sounds like both of you are talking about the AVR Line. I believe that this is a leased line still owned by CSXT. I think it was actually the P&W Sub under CSXT, and it still retains that name under B&P. Not sure about AVR. The AVR runs to Bakerstown to interchange with the B&P. Sometimes they will do the interchange at Evans City pending train length. The B&P has the same line from Bakerstown to New Castle.