Abandoned elevated line Phili 30th Street Sta?

Mr. Jim Boylan is correct, the bridge to which OP actually refers is the former 52nd Street Flyover. This interlocking is currently called CP PAXON, CP VALLEY, and CP JEFF (it was split into three interlockings following the closure of the flyover). The flyover itself was host to the westbound Schuylkill Branch platform at the former PRR 52nd Street Station, which was closed due to a fire some time in the late 20th Century.

Fun fact: Amtrak offered to put in a new bridge for SEPTA, but they turned Amtrak down in preference of building out the old freight connection track instead.

So why was the bridge taken oos?

Word circulating at the time was that the bridge had deteriorated to the point that it would soon have to be either taken out of service or undergo major renovation, and since its original reason for existence was to bring westbound passenger trains (everything from the Broadway to MU Norristown locals) up and over the once-heavy freight traffic between a yard just east of there (now gone) and the two center tracks of the four-track line to Paoli and west, it made more sense to stay on the ground as described by Mr. Boylan and avoid the bridge altogether. Many times, passengers on westbound trains going over the bridge could look down and see a long freight drag pulling in or out of the yard, but not any more -- the freight moves over the former Reading now. I didn't know that Amtrak had offered to rehab the bridge -- I thought they just told SEPTA "we don't need the bridge any more -- if you want to keep it for an occasional one-car Cynwyd local, you fix it."