Dave & Ken,
Trying to decipher Gen. Notice 207 on clearances. The PC book does not show a restriction on the mainline between Conway and Pitcairn. The PRR book gives you alot more information but it is a bit hard to figure out. There is a 17'-9" and 18'-6" restriction between Island Ave and the Pgh Station.
They would be the overhead bridge at PENN, O.H. walk ways between PENN and Federal St, the Fort Wayne bridge and the Pgh station roof. There should be another just east of Swissvale at Hawkins.
These are good for todays tri-levels and truck-trains but not double stacks. I don't know what was ever done at these locations to get the tri-levels through when they came to being used.