While recently searching around for information on Reading towers, I came upon an interesting resource relating to an interesting manual block scheme employed by the PRR on their Schukyll Valley line between Philadelphia and Reading. This line was one of several built in the late 19th century as part of the PRR's feud with the Reading. Intended to stab into the heart of Reading territory the line didn't have quite its intended level of success, but ultimately winding its way to the Scranton area, the route was seeing about 18 passenger and 8 freight trains per day in the 1930's.
|Click to Enlarge|
Unlike the Reading's 2-4 track ABS main line, the PRR's attempt of competition was mostly single track with passing sidings operated under manual block rules. On the twelve miles of the line centered on Birdsboro, PA there three passing sidings, each requiring a manned block station that in the depths of the depression, even the likes of the PRR couldn't afford. While the technology to CTC this type of line had been debuted by the NY Central in 1927 and was also being deployed by the PRR at THORN and COLA, the powers that be decided on a more cost effective solution.
|BROOKE tower, note both the PRR and Reading signs.|
The jointly PRR/RDG operated BROOKE tower in Birdsboro controlled a crossing between the PRR line and the Reading's line to Wilmington as well as a number of other local yard and industrial tracks. There was no way this tower could be eliminated to the PRR installed a 20-lever table interlocking setup to remote control both the local BROOKE siding and one additional siding in either direction. However if you think that sounds like CTC...you would be wrong.
|The 20-lever table setup had been reduced to 8 by the 1970's.|
First, as far as I can tell the system was direct wire, not some sort of remote code system as one would expect from CTC. More importantly, there was no traffic control, which is two of the three words that make up the term CTC. The operator at BROOK would use the levers to work the remote switches as well as the manual block signal granting access to the next block. Track occupancy lamps on the table units would confirm the passage of the train. In fact almost the entire line was covered by track circuits and distant/home signals would provide full block status between themselves and the next manual block entrance (Stop and Proceed being substituted by Caution).
Despite being a bit of a kludge, the system was successful, operating until BROOKE was closed in 1977. It allowed the PRR to close two manned Block Stations and paid for itself within 3 years. Why they didn't just go for CTC is still a mystery. After all the tracks were circuited and the sidings signaled and under remote operation. My theory is that the PRR was just very conservative when it came to its focus on reliable operation and didn't want to gamble on a technology was not yet fully established.