Through freight operation on the GC&SF

In this article I hope to explain the logic behind and operation of the 'through freights' on my GC&SF layout.

An Operating Session on the GC&SF represents an 18 hour work-day, and is scheduled to take three hours using a 6:1 ratio 'fast clock'.

On each 'day' I schedule 14 main line through trains:
- 4 x Class 1 passenger trains (2 running from staging to staging, in each direction);
- 4 x "through freights" (2 running from staging to staging, in each direction); plus
- 6 other mainline freight trains to service specific traffic types (livestock, oil and grain).

(There are also several other local freights and mixed locals, but they are outside the scope of this article.)

This is the timetable that I've developed to manage the orderly movement of the through trains during a session:

In order to prepare that timetable, I first had to create a train graph to plot the movements of my through trains, and where and when they'd meet. Here's the first part of the train graph:

What do I mean by 'through freight'?

In this context I'm referring to trains that operate between major yards, etc. hundreds of miles apart. As they travel down the line they stop at principle yards to:
(i) set out blocks of cars which will be forwarded to their destinations by local freights; and
(ii) pick up blocks of cars for delivery to destinations further down the line.

The through freights on my GC&SF loosely represent the real AT&SF "Fast Freights" nos. 37, 38, 39 and 40 that operated between Texas and Kansas (and beyond).

The simulation

Each of my through freights is typically two locos, 20-22 freight cars and a waycar. At the start of a session, southbound Trains 37 and 39 are located in north staging, and northbound trains 38 and 40 are located in south staging.

The Train Cards for each train are double sided. Those for Trains 37 and 38 show Train 37 on one side, and Train 38 on the other. Likewise, the Train Cards for Trains 39 and 40 show Train 39 on one side and Train 40 on the other.  At the start of a session, each train (37 to 40) is represented once and only once. For example, southbound Train 37 starts its 'day' in north staging. At the scheduled time it leaves staging and runs to Pauls Valley, where it sets out and picks up a few cars. It then runs to Ardmore where it again sets out and picks up cars. Finally it runs to south staging. Before the next session I 'turn' the train card to show Train 38, and also turn the waybills for the cars that exited the layout in the previous session.

The details

Each through freight will have 20-22 cars at the start of a session, and approximately one-third of those cars will be selected to be set out during the session. The other two-thirds are treated as though they are for destinations further down the line (notwithstanding the fact that their waybills indicate otherwise). The Train Pack is arranged to indicate which cars are to be set out, and which will 'run through'.

Operationally, the freight cars to be set out are the front-most 6 - 8 cars, while all cars that depart for staging are added to the rear of the train. This ensures that cars cycle through the train.

To illustrate this 'cycling', imagine a session starts with a flatcar sitting at Wynnewood Engineering in Wynnewood, with a load for a customer somewhere up north ("offline north"). During the session ("session 1") the flat car will be collected by the local freight and delivered to Pauls Valley. The Pauls Valley yardmaster will add it to the rear of northbound Train 38 when it passes through, and Train 38 will retire to north staging.

Between sessions I will turn the Train Card, and (former) northbound Train 38 will become southbound Train 37 for session 2. I will also turn the flat car's waybill as its load will be deemed to have been delivered.

When Train 37 comes online in session 2, the flatcar will be in the rear third of the train, and for the purpose of the exercise it is considered to be heading to a location further south. As the train moves across the layout, it will lose cars from the front, and add a similar number of cars to the rear. By the time Train 37 reaches south staging, our flatcar will have advanced to somewhere in the middle of the train.

During session 3 our flatcar will again be northbound in Train 38. It will start the session in the middle of the train, but will be located in the front third of the train when the train reaches north staging.

Finally, in session 4, the flatcar will be cut out from southbound Train 37 when it reaches Pauls Valley, and the local freight will move it to Wynnewood Engineering.

My 2-way waybills lock cars into repeating cycles between an online industry and an offline destination, but I'm not worried by that. As I've explained, a car will only return to its online customer once every four or more sessions, so the repeating cycle isn't all that obvious. Besides, many real freight cars were fitted for specific customers, and hence locked into similar cycles.

Well, I hope that explains it, but if you have any questions feel free to email me at:
gulflines @ (remove the spaces.)


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