I am the retired General Counsel of Conrail, the company that used to own the part of the viaduct that is now completed. When I first walked over to look at it, I couldn't understand why the so-called City Branch (which came down from Fairmount Park, under Broad Street, and then ramped up to the Viaduct) created a Y where the 9th Street Branch (the longer, unfinished piece) ended where it did and how it was used decades ago. I then realized, looking where it ramps down next to the old Reading Building adjacent to the park (currently a host for computer servers) that the trains would back down to the building to deliver small packages to the former Reading parcel post and administrative building. The train would then push the empty cars back under Broad Street through the undercut of the City Branch passed the Inquirer Building back to the Park. Being a train geek, it was really an epiphany for me and made me appreciate the infrastructure even more than I already did.