Just south of the Hills station, the PRR track crosses the Chartiers creek to parallel the Montour Railroad's track on the other side. The Montour track sits at a higher elevation than the PRR's track. As both tracks continue in a southwesterly direction, there are two tunnels. From the map below, you can see the Chartiers creek snake around a sharp ridge line. When the PRR built the Chartiers branch, it decided to dig a 500-foot tunnel through this ridge. The surrounding land was owned by the Bells family, and so the tunnel (the only one on the Chartiers branch) was called "Bells Tunnel". Several decades later when the Montour Railroad built their track in the area, at a higher elevation, thus crossing over the Chartiers branch via a Warren Truss bridge just tens of feet away from the northern/eastern entrance to the Bells tunnel, it, too, built a tunnel, which was 235 feet long. The land around their tunnel was owned by the Greer family at that time, so they named theirs the "Greer Tunnel". By the way, after the south/west tunnel exit on the Montour Railroad, that railroad crossed over the Chartiers creek via another bridge, so they had a bridge, tunnel, bridge scene. Both various topographical maps, as well as railroad timetables, have mislabeled the tunnels. The PRR called it the Bells tunnel, while the modernday Pittsburgh & Ohio Central calls it the Greer tunnel, adding even more confusion. On this web site, I will call the PRR's tunnel the Bells tunnel.
Today, the former Montour RR track is called the Montour Trail. The Montour Trail was completed in 2008.