Straddling the towns of Middletown and Royalton in Dauphin County, Royalton interlocking was a strategic point where most freight and passenger traffic separated for the trip east to New York, Philadelphia and Baltimore. Approximately 10 miles east from State Interlocking the mainline and Columbia branch (today Norfolk Southern's Royalton branch) ran along side each other with the freight operating on tracks furthest to the north. The Columbia branch, which drops south along the Susquehanna diverted freight trains away from the main at Royalton requiring traffic to cross into the path of the busy passenger main. To avoid this potential traffic disruption the PRR applied a proven technique of building a fly-over to allow all tracks/trains to gain proper position without the need to physically cross or intersect the other route.
Prior to the late 1950's Royalton interlocking was controlled by a two story frame tower that sat on the eastern side of the tracks (railroad was oriented north - south here). The early interlocking plant was of an older design using a mechanical armstrong complex to control the switches and signals between the mainline and Columbia branch. The Columbia branch served as a back road connection from the mainline and freight yards in Harrisburg to the low-grade route via Shocks Mill allowing freight from all directions to bypass congestion in Enola when necessary. In the late 1950’s Royalton interlocking was made a remote facility named Roy with control given to the operator at State Tower in Harrisburg. Evidence of this project survives in the form of a single story relay house that rests on the foundation of the former tower. As part of Amtrak’s Keystone Line rehab, Roy was rebuilt once again providing Amtrak with a set of crossovers for operational flexibility (the line is now governed by Rule 261-allowing bi-directional traffic flow) while maintaining the connection to the Royalton branch.
Special thanks to Mr. Don Rittler, who's input on operations at Royalton provided some insight on this relatively obscure facility on the Pennsylvania Railroad. Don worked as a tower operator for the PRR and its successors in the Harrisburg region from 1937-1979.