Freight Operation using Dice

This article first appeared in the March/April 1989 issue of AMRA's 'Journal'.
By Steve Chapman.

If you want to operate your model railway in a realistic manner then each move made by a train (I include lone locomotives) must have an apparent reason for each move that it makes. Train movements can be broken down into a number of categories in order to determine what sort of movements would be required, these include (but are not limited to) -

  1. Through passenger (not stopping)
  2. Through freight (not stopping)
  3. Stopping passenger.
  4. Terminating passenger.
  5. Local freight.
  6. Locomotive movements.

The problem is deciding what movements to make so as to make each of these trains appear to make realistic movements while on show on the layout. Through passenger and freight trains which do not stop are not really a problem in that they leave the fiddleyard (or whatever), pass straight through the station without stopping, and disappear from sight again (to hopefully appear again later travelling in the opposite direction.

Stopping passenger trains are not much more difficult than the non stopping variety. All that happens in this case is that the train slows as it approaches the station, stops at the appropriate signal (which would normally put the train next to the platform - but not necessarily), and then after a suitable pause (during which time the signal should be cleared if it wasn't already) sets back off on its way.

Terminating passenger trains involve more train movements (including in most cases locomotive movements). At the very least (unless the train is a multiple unit or a push-pull) the locomotive must be uncoupled and either another locomotive coupled to the other end or the original locomotive must be run around the train. Additional moves can be made by taking the locomotive to the coaling stage to take on coal, placing the locomotive "on shed" and replacing it with another locomotive, or a variety of other locomotive movements which can be determined to suit the circumstances.

Locomotive movements are relatively easy to work out. All you have to do in this case is come up with a plausible reason for shifting a locomotive from point A to point B. Perhaps the number of locomotives passing through the station in one direction is not balanced by movements in the opposite direction and a light engine movement is required to balance it out, and there are of course the movements associated with the terminating passenger train.

None of the above train movements is difficult to work when someone makes an effort to plan realistic movements. The type of train movement which gives the most part of the trouble is the local freight train. Local freight trains are broken up and reformed or at least drop off and pick up wagons at goods yards along the way. How can we realistically decide how these trains are to be operated.

Again we can break the problem down into a number of different parts which can be considered separately.

  1. Allocating purposes to each of the wagons on the layout.
  2. Deciding traffic frequencies for various types of freight.
  3. Deciding which sidings at a station are to serve what purpose.
  4. Deciding which wagons are to be included in which train as it approaches the station.
  5. Deciding which wagons are to be dropped by the train at the station.
  6. Deciding which wagons at the station are to be picked up by the train.
  7. Deciding where in the train that wagons which have been picked up are to be put.

Again some of these things are easier to determine than others. Each of the wagons on the layout will be of a particular type (eg flat wagon, open wagon, van, tanker) and will have one or more obvious uses to which it could be put. These uses can be listed.

Each use to which a wagon can be put can be assigned a frequency (eg one a day, fifty a day, once a month, rarely) simply by looking at the type of service that you intend to model. This can either be based on the type of services run by the railway company on which your model is based or can be worked out to suit the rolling stock available.

Deciding which siding is to serve what purpose will possibly have been worked out when the layout was planned. If it wasn't then perhaps it will be obvious because of having a particular industry next to it. If neither of these cases apply then you might need to thing about it for a while before deciding what various sidings are to be used for.

track diagram

Having determined these things a card for each wagon can be produced listing each of the siding locations at each of the stations at which the particular wagon could be expected to be found (and lightly in pencil the percentage chance of finding the wagon there can be indicated).

example wagon card

Deciding which wagons are to be included in which trains can be determined if movement frequencies can be determined for each wagon. This is determined from the traffic frequencies and could be indicated by ranking the wagons by placing a number between one and six in the top right hand corner of its card (where six indicates frequent movement and one indicates infrequent movement). The wagons to make up a particular train can then be determined by first deciding how long the train is to be. Then stack the cards for all of the available wagons in a pile and get out your dice. Throw one and count down the pile of cards the number indicated placing the cards removed at the bottom of the pile. If the number thrown was not greater than the number in the top right hand corner of the card then the wagon to which the card belongs should be included in the train. Repeat until sufficient wagons have been selected to make up a train of the desired length. This method will give a train of semi-randomly selected wagons (allowing for their determined frequency of operation) and will avoid having all local freights look exactly the same.

Deciding which wagons are to be dropped off at the station is where the list of siding locations on the card comes in (one of the options - and perhaps the one with the greatest individual frequency -should be that the wagon goes straight through). Based on the percentage frequencies shown numbers between one and six (or perhaps double numbers 11,12,13,14,15,16,21,22,23,24....56,66) can be listed next to the options such that all combinations are listed and the percentage chance of a particular option coming up is approximately what was originally determined.

An alternative to this is to use percentage dice. (Percentage dice are two twenty sided dice with the numbers one to ten occurring twice on each. The two dice are different colours so that one can be identified as the tens die and the other as the ones die.) Work out percentage numbers for each line by summing all of the percentages above each number and adding the sum thus obtained to it (eg option1 = 5%, option2 = 7% then option1 has percentage number 5 and option2 has percentage number 12).

One or two dice can then be thrown and the appropriate location for each individual wagon in the train can be determined (in the case of using percentage dice by finding the first option whose percentage number is not less than the percentage thrown). So now we have semi-randomly generated information regarding the destination of each wagon within our local freight train. The train can be shunted when it arrives at the station so as to get the wagons to the specified locations. The destination of each wagon can be kept track of on the card by placing a paper clip next to the selected entry.

This has handled the arrival side of the freight operation and leaves us now only with the task of having to determine the departure side of things.

So next to decide which wagons are to be picked up by this train while it is in the station. This can be done by determining firstly how many wagons are to be picked up. This might be the same number as was dropped off, a number randomly selected by a dice throw, or might possibly be based on how long wagons have been sitting at the station. If a specific number of wagons is to be picked up then the same selection method as was used to determine what wagons went to make up the train in the first place can be used (but this time using the cards belonging to the wagons currently at the station - either including or excluding the ones just dropped off).

The only thing left to be determined is where in the train that the wagons being picked up are to be put. This can be determined by a number of methods. The simplest method is to put all of the wagons picked up at the front or rear of the train (with the supposition that they will be shunted at a subsequent station). Alternatively, if the station has a sufficiently large goods yard to allow shunting relatively easily, (or if you want to add more shunting moves,) then throw dice for each wagon being picked up (you must also have done this originally for each wagon which is in the original train and is passing straight through) to determine how far down the line that the next destination for the wagon is and to shunt the wagons so that all of the wagons for the same destination are together. It doesn't matter whether you shunt all of the ones to the back of the train and all of the sixes to the front, or whether you do it the other way around.

This takes care of almost everything. If you have a terminus to fiddleyard layout then there is no problem as all wagons in the train should have destinations at the station. A brand new freight train can then be put together to run in the reverse direction. If you have a through station though the above method of generating freight movements will feed trains into the fiddleyard from both directions.

The direction from which each wagon entered the fiddleyard needs to be kept track of so that you know which wagons are available to make up trains to run in each direction. The idea is that any rolling stock that entered the fiddleyard from one end should depart from the same end. (There are exceptions to this if using one item of rolling stock to represent more than one, or more than one to represent the same one for loaded and unloaded versions.)

If local freights in each direction are evenly balanced then there should normally be no problem with all of the freight stock accumulating at one end. If a greater than average number of wagons finds its way to one end then there is still a relatively simple solution. The solution is to include a number of optional through freights when setting up your timetable. Now before too much stock accumulates at one end an optional train can be run which transfers the surplus wagons back to the other end of the line.

So there you have it, a method of operating your local freight trains which looks realistic, is relatively simple and cheap to run, and which adds enormously to the operational interest of the layout.

And for those of you sufficiently rich to be able to afford a computer, a computer program to carry out the above should not be very difficult to write (and if enough people are interested I might write one).

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Copyright Stephen Chapman