DJ of DJsTrains
May 19, 2022
The P&LE in it 'hey days' used to have 3 and 4 tracks in various locations as the mains between McKeesport and West Pittsburgh were double track. It is amazing what facilities operating steel mills and running passenger trains for the B&O and for the P&LE itself require. What the remnants of the P&LE that exist today are pale imitation of what once was.
The first arrangement was single track, then railroads went to "double track.", especially on passenger routes.
Double track is not the same as two main tracks, different operating methods.
Some railroads with very heavy traffic (mostly in the east coast and mostly around major terminals) went to 3 or 4 tracks, but the vast majority of tracks were one or two main tracks.
Originally double track was very common, which is current of traffic, trains run in one direction and is signaled in one direction on one track and run in the other direction and is signaled in the other direction on the other track (operated by rule 251). The direction against the current of traffic is dark (has no signal system). Double track can handle a huge number of trains and is very efficient, as long as everything moves at the same speed and nothing goes wrong. However it becomes very awkward when you have to cross trains over and mover them against the current of traffic.
When CTC was invented in the 1920's, it was a HUGE step up in capacity since it uses two main tracks, both signaled in both directions. That hugely improves the flexibility. Faster trains can easily be routed around slower trains and if something goes wrong on one track, trains can easily be routed around the problem on the other (MUCH more difficult in double track).
CTC actually improved the operation so much many lines went from two main tracks to single track with sidings or went from 3 or 4 main tracks down to two main tracks. CTC really expanded in the 1960's and 1970's, and current of traffic and ABS/Timetable and train order/track warrant was extensively upgraded to CTC in the 1990's and 2000's.
One thing that gets overlooked by many when operating territories with two main tracks, Most all two main track territory was laid out when Current of Traffic Signal rules were in effect - West on #1 and East on #2 or whatever individual carriers called their tracks. Because of the signaling industry spurs would be constructed as trailing point affairs from the track that connected to the Main track - either #1 or #2. When CTC - bidirectional signaling was installed on prior current of traffic signaling - the location and direction of spur tracks from those mains remained the same. Yes - you can run trains with signal indications on either track, however, if you are operating a train on what would have been 'against the current of traffic' the options to handle bad order cars is drastically diminished. New Dispatchers learn this the hard way.