Zoo Interlocking (Philadelphia) to Parkesburg

Zoo Interlocking (MP 1.9) is a large double-overlaid wye, connecting the tracks southeast to 30th Street Station (both low-level and high-level) on separate tracks, with the latter west of the former, with the tracks northeast to North Philadelphia (and New York City) and the tracks northwest to Parkesburg and Harrisburg. The elevated tracks from 30th Street High-level cross over the west leg of the low-level wye just north of its south apex, after which the higher-level tracks have their wye within the confines of the lower-level wye, with the added complication that there is a flying junction separating the tracks by direction at the northeast apex of the wyes. The speed limit is 30 mph through the wyes and interlockings at Zoo. The tower once stood on the north side of the south-to-east leg, lower level.

Now double track, the overhead AC electrified line heads northwest, with speed limit 60 mph, past bridges over streets crossovers at Stiles (MP 3.5), at Valley (MP 4.0), where the SEPTA Ivy Ridge line departs to the north on a flyover with a through bowstring truss bridge, followed by the SEPTA Ivy Ridge maintenance facility on the north side, with a line trailing back in at the west end, a road bridge overhead, and crossovers at Paxon (MP 4.1), a bridge over a street, extra track on the north side, and through  the western Philadelphia suburbs along the so-called "Main Line", past a gentle curve to the north-northwest at the crossovers (where four tracks start) and passenger station with two side platforms at Overbrook (MP 5.4), where line speeds of 70-35/25 start, and north at the passenger station with two side platforms and a depot on the north side at Merion (MP 6.0), past three road bridges overhead, then northwest (with 60 mph passenger speed limit on the curve) at the passenger station with two side platforms at Narberth (MP 6.8), where there is a bridge over a street at the west end and freight speeds rise to 35/30, west to the passenger station with two side platforms and a depot to the south at at Wynnewood (MP 7.5), northwest past a road bridge overhead, a spur trailing in on the north side, the passenger station with two side platforms at Ardmore (MP 8.5) a bridge over a street, and the passenger station with two side platforms with shelters and a depot to the south at Haverford (MP 9.1), MP 10, a bridge over a street, the crossovers within the station area and passenger station with two side platforms at Bryn Mawr (MP 10.1), a road bridge overhead, a bridge over a street, and the passenger stations with two side platforms and depot to the south at Rosemont (MP 10.9) and with two side platforms at Villanova (MP 12.0), with a road bridge overhead at the west end followed by an Interstate highway below.

The line curves west, bridging over the Norristown High Speed line, and past the passenger station with two side platforms and depot to the north at Radnor (MP 13.0), Intermediate Signals on a signal bridge, the passenger stations with two side platforms at St. Davids (MP 13.8), and with two side platforms at Wayne (MP 14.5), a bridge over a street, a road bridge overhead, and the passenger stations with two side platforms and a depot to the south at Strafford (MP 15.4), where there was once a connection on the south side from what is now the High Speed Line, a bridge over a street, a road bridge overhead, detectors for both directions at MP 16.3, the passenger station with two side platforms at Devon (MP 16.5), a bridge over a street, the passenger station with two side platforms and a footbridge overhead at Berwyn (MP 17.5), a road bridge overhead, MP 18, the passenger station with two side platforms at Daylesford (MP 18.6), a bridge over a street, and the passenger station with two side platforms and a depot to the south at the crossovers (with a signal bridge, where four tracks end, with speed limits of 65/60-30-20 in the interlocking) at Paoli (MP 19.9, terminus of many SEPTA trains, where there is a closed signal tower on the north side, and a SEPTA yard on the north side of the line west of the station. Continuing west, with speed limits now 90-50/40, except 75-40 on some curves, the line passes a bridge over a road, a street alongside to the north, the passenger station with two side platforms at Malvern (MP 21.6), crossovers at Frazer (MP 23.9), where a line departs on the north side, there is an eastbound detector and a PRR line once crossed from north to south (and a present-day line passes beneath from NE to SW), a bridge over a street, a road bridge at an angle overhead, and crossovers at Glen (MP 25.3), where a former Conrail track trails in and the line becomes three tracks wide, with the third track (track 2) having only a 30-25 speed limit while the others are 90-50, passenger stations with two side platforms at Exton (MP 27.5) and at Whitford (MP 28.3), where a freight line bridges overhead from the northeast to the southwest, two bridges over streets, a road bridge overhead, extra track on the north side, a road bridge overhead, crossovers at Downs (MP 32.1), where a former reading line from Norristown trails in on the north side and four tracks start (the additional track 3 is 60-40 to add to the existing speed limits on the others), a bridge over a street, the passenger station with two side platforms at Downingtown (MP 32.4), a bridge over a street, a street alongside to the north, crossovers at Thorn (MP 35.0), where a fifth running track starts, and at Caln (MP 36.6), where it ends and there is an old tower on the north side, a passenger station with two side platforms at Coatesville (MP 38.4), a road bridge overhead where the road alongside crosses, westbound detectors at MP 39.0 (hot box), three bridges over streets below, and 39.9 (dragging equipment), a bridge over a road, a bridge over a north-south rail line, a road bridge overhead, two bridges over streets, crossovers at Park (MP 43.9), where four tracks end and speed limits on the through tracks are 70-40, and the passenger station with two side platforms at Parkesburg (MP 44.2), the west end of SEPTA service.