I’m modeling, 1955 era (mixed diesel-steam era), an imaginary secondary mainline with a junction with two branchlines. The mainline is operated “blind,” that is, no CTC but with timetable and train orders. I’ve built an interlocking tower, but don’t know if locating this structure at such a junction would be “prototypical” of Southern Pacific Railroad practice.
Mainline traffic will typically consist of (1) a daily round-trip express/passenger train, (2) twice-weekly round-trip coach/pullman passenger trains, and (3) about six freight trains in each direction. In addition, the first branchline will usually have two round trips (mineral and general freight), while the second (to a military base) will usually have about one. Almost all of the branchline trains will originate from a division point about thirty miles south of the junction.
The junction consists of (1) a passing siding about one mile long, (2) at the south end there is a passenger/freight depot and a house/team track siding, (2) at the north end, there is a turntable and locomotive servicing track for helper locomotives for the grade north to a pass, and to service and redirect branchline trains to the branches as needed. Schematically, the junction looks like a backwards K, with the mainline running north/south, and one branchline heading northwest, and the other branchline heading souwthest. The branchlines intersect the mainline about in the middle of the siding. The siding junction’s double-ended siding is “lapped,” that is, there is a crossover connecting the siding in the middle, just south of where the branches meet the mainline. The depot is manned 24 hours a day and is about a quarter mile south of the junctions. If I was to have an interlocking tower, the middle of the siding where the crossover and branchline junctions are located, would seem to be a logical location.
So, specifically, (1) does the traffic justify the expense of a tower and its additional personnel, and if so, (2) what portion, if not
Typically, a crossing for important junction will have a signaled interlocking. Since you have a cross-over and jct switch there, that would be a good reason for the tower. This would be logical/prototypically accurate. Modeling the ‘pipe/rods’ from the tower out to the switches/signals would make a very interesting detail.
My layout has ‘dark’ railroading as well, but I do have a signalled crossing with working home/distant signals planned for installation as soon as I get some other scenery stuff in the area completed. I love to watch the older semaphore signals in action! BTW, even with ‘dark’ railroading, you need ‘train order’ signals at your stations - another excuse for some mild signalling…
In your scenario, to give an example from my home town in southern Illinois, someone in the depot would serve the function of interlocking and there would be no tower dedicated to that purpose.
Yes,you will need towers along the way to control help control traffic…Plus you will need a dispatcher.Your towers would be at EACH junction for traffic control.
The type of signal will depend on the railroad you are modeling or if a freelance railroad then the type of signal that suits your fancy.
To add to this - Since the actual ‘junction’ is at least a 1/2 mile from the end of the siding/depot, an operator manned interlocking tower would make sense. I worked as an agent/operator/leverman in the late 60’s, and pulling a lever that controlled a switch over a 1/4 mile away took some real work! Having a ‘manned’ tower with an train order operator half way down a ‘lap’ siding/jct would make a lot of sense. It would also make sense having the end of siding switches ‘spring’ switches as well. That way the operator could use the interlocking at the mid-point/jct line trains into the siding(under dispatcher control) and deliver train order for meets, and trains could leave the siding after a meet without stopping to line the switches back to the main track. Sounds like an interesting operation for one of your operating crew!
Thanks for your input. After considering your input and doing research on the local Southern Pacific San Ramon branch (1891-1978) (Irma Dotson’s 1991 book titled San Ramon Branch Line of the Southern Pacific), I’ve concluded an interlocking tower would likely NOT be prototypical on my trackplan. This branch connected to its parent Southern Pacific twice: at its north and south ends, both with wyes. The north end did not have an interlocking tower, but the south end did have one.
The north end was at Avon, about three miles east of Martinez (Martinez is on the SP, now UP line from Oakland to Ogden via Donner Pass) on the Mococo Line which went east to the Central Valley via Antioch and Byron. (Mococo for Mountain Copper Company, Ltd, that was located nearby.) There was a small, one-story cottage type depot there from 1901 to 1964, located on the mainline at the west end of the wye.
The south end was at Radum, attaching to the SP’s line between Niles Canyon to the west and Altamont Pass to the east. This mainline connected the South San Francisco Bay to the Central Valley. The Altamont Line eventually connected with the Mococo line east of Tracy in the Central Valley.
The San Ramon branch reached Radum in 1909 when SP extended the branch south from San Ramon. By this time the Western Pacific had built its mainline paralleling SP’s Altamont Line. To reach the Southern Pacific track, the San Ramon branch had to cross the WP track at two places where the WP crossed two of the wye’s legs. An interlocking tower was built within the wye at the west end in 1911. An SP community relations official said the SP had no record (about the construction?) of the Radum Tower and that the tower was jointly owned with WP. There was no depot building there, but an old baggage car was located adjacent to the tower and parallel to the mainline. In 1931 SP usually manned the tower six days a week (not Sundays) for eight hours: 7 a.m to 12 noon and 1 p.m. to 4 p.m. There were some periods when ther