5. Wagon Load Generation

This article is closely based on one published in Narrow Lines and some information is slightly out of date by now. The general principles still hold good.
  
  
The previous articles have broadly examined the framework within which a freelanced model railway can devise a credible background operating scenario. Having reached this point, even if they have not closely considered these parameters, many modellers are content to loosely run trains within these constraints. Goods trains are goods trains, after all, and as long as they contain goods wagons, for many modellers this is sufficient, ditto for passenger trains and carriages.

Unfortunately this ad hoc method of working ignores the very purpose of the railway. The prototype was a business enterprise that provided a transport service. It responded to the demands of its customers, the most important of whom were goods shippers. There were fluctuations in the nature and quantity of goods offered for transport consequently the railway had to react to their requirements. Traffic varied on a daily, weekly and a seasonal basis, one obvious example being the market day rush, and the peaks and troughs were most marked on the NG feeder line built to serve an agricultural area. Whenever the scheduled trains were unable to cope with the additional traffic extra trains were run providing a credible, rather than concocted, excuse to run a special service. If we wish to replicate the true nature of railway working it is necessary to stop haphazardly throwing trains together on a whim and create a traffic generator which will simulate these diverse demands. Once again this is an approach traditionally associated with American modelling but articles have sometimes appeared in the British press outlining the principles. In effect the individual items of rolling stock become pieces in a complex game and the temptation to cherry pick the nicest or newest stock and assemble it into an aesthetically pleasing but ultimately pointless generic train is avoided. The possession of a large layout is not a pre-requisite for the implementation of such a scheme and I have attempted in this article to show how the system can be tailored to suit the typical NG layout. The original Fenditavalat was always  operated using these principles. 

For those interested in the application of this system to a small layout a section has been created at Operating the original Fenditavalat which can be accessed by pressing the button below.




Operating the original Fenditavalat
  
A typical seasonal extra crosses the Kasatritikakamparoj in September taking SG hopper wagons to Boursson to be filled with the recently harvested grain. This photo was taken a few sessions ago and the foreground scenery is now finished.
  
  
The first stage in devising such a generator is the consideration of the traffics likely to be offered at each model station's location. The AFK is a large system and the line crosses a diverse range of landscapes which, as noted, was a deliberate choice made to create an impression of the distance travelled and to ensure that the contrasting economies generated the traffic necessary for a successful railway system. There are approximately 130 traffic flows listed in the AFK traffic book but if we examine Boursson this will demonstrate the basic methods applied to a simple station. Boursson is a compact through station and, when it is viewed in isolation, the rest of the layout simply functions as the equivalent of two fiddleyards, similar to many smaller layouts, albeit that these may be combined in a series of loops on the other side of the room..

Boursson, of course, is a non existent community on a freelanced railway set in an imaginary province of a fantasy country. If we are to create a credible model with realistic traffic flows it is necessary to establish a coherent geographical background for the station and to understand its economic hinterland. It is envisaged that Boursson serves a number of small villages situated on the Kasatritikakamparoj plain and deals mainly with agricultural traffic. Rather than being the focal point of the layout, Boursson is a wayside station and a large number of trains pass through without stopping although two local goods trains each way do shunt here. Boursson’s infrastructure is typical of the small stations previously examined although dead end sidings serve the Syvrone canning factory and the agricultural Co-op. Most British stations were capable of dealing with all traffics and it was common to find the ‘standard’ list of goods shed, cattle dock, crane and coal staithes, although the equipment provided at each location varied, hence the need for the RCH handbook of stations. This, amongst other things, listed the crane capacity and showed whether livestock could be handled. Boursson reflects continental NG practice in that the cattle pens are absent, because animals are loaded directly into wagons from the goods bank, and the coal staithes are missing, presumably because firewood and animal dung provided domestic fuel across much of impoverished rural Europe during the NG era.
  
  
The Syvrone canning factory is an important source of traffic for the AFK. In reality many of the wagons are stored on a shelf below the layout with the siding acting as  open staging
  
  
Within this context the outward traffic flows can now be established. Cereal traffic predominates with wheat being exported from the AFK via the quayside at Eromarbordo or the SG transhipment point at Relforka, (which would effectively equate to the down fiddleyard on a smaller layout). Malting barley provides another flow, and is forwarded to Karamspur brewery or that at Bitrano on the CFS, both in the up direction. Canned goods mainly go to Relforka, although numerous other destinations are also listed, and the area additionally supplies pigs to the slaughterhouse at Lacono on a regular basis. As might be expected in an agricultural community seasonal traffic flows predominate and, at the appropriate times of the year, sugar beet, potatoes and cattle are forwarded. There are other outward flows but these need not concern us here. The inbound goods can comprise anything within reason, although the two most common are ‘agricultural supplies’ and ‘consumer goods’. These are obvious catch-all phrases to cover the multitude of smaller items, ‘the ales and mails, hat boxes and fish boxes, prams and rams’ that were consolidated into the single wagon loads which turned up at wayside stations. (1) These and other loads are generated from a complementary list of traffics at Relforka, which would be the down fiddle yard on a smaller layout. The canning factory receives specific goods, such as cans, vinegar in bulk containers and coal as well as taking fruit and vegetables from other stations on the agricultural plain. The flows at the other AFK stations were analysed in the same manner and any-one looking for additional traffic ideas would do well to obtain a copy of The Classification of Merchandise on the secondhand market. (2)
  
  
Seasonal traffic flows, The large Co-Co works SG bogie wagons during the sugar beet campaign at Boursson.
  
  
Having established the flows it is necessary to simulate them, but a word of warning may not be remiss here. As was noted in Section 1, NG lines were built into areas that offered thin prospects. A common pattern was to find that a large quantity of outward bound low value goods, from the extractive or farming industries, were transferred at the SG junction with little traffic returning into the interior, the imbalance saddling the NG with a large amount of unremunerative mileage as many wagons were returned empty for their next load. This pattern was attenuated where the NG served an extractive industry in an upland area. Lines such as the La Mure system, built to service coal mines in the Alps, or the Festiniog and Talyllyn, serving the slate quarries, had little expectation of significant inbound traffic. Similar patterns were apparent even on the NG common carrier lines. Outgoing timber on the CFD Vivarais system accounted for over half of the traffic and the area also produced sufficient outbound ‘early’ agricultural products, such as cherries, apples and peaches to run special trains connecting with their Paris-bound SG counterparts, as well as large quantities of stone. It was estimated that inbound traffic formed only 10% of the revenue, with a slightly improved 4:1 imbalance being noted for the Reseau Breton. It would be easy, and prototypical, to simulate such a pattern without difficulty on a simple fiddleyard based layout but one of the fundamental concepts on the AFK was that, rather improbably, there would be many movements between on line industries which would involve the transference of wagons between trains at Lacono. When it became apparent from the initial test runs that a one-way pattern was emerging certain industries were physically relocated to counter this trend and to ensure that local trains in the KTT had to attach as well as detach wagons in both directions.
  

Lacono's shunter deals with a raft of NG and SG wagons, many of which are being transferred between services in the small yard at Lacono. Once again this might be a practice more appropriate for a standard gauge layout rather than a narrow gauge one
  
Now that we know what Boursson produces we need to determine how the loads will be forwarded. Most operationally orientated American model railroads use one of two systems, the 4 cycle waybill (consignment note) or the coloured tab. At a basic level these are simple to devise and are self perpetuating once set up but they are not used by the AFK. The systems are reviewed frequently in magazines such as Model Railroader for any-one interested in using them but both systems are orientated towards simulating American SG railways and have drawbacks for the small NG system which are not immediately apparent. The problem is that SG vehicles which were free to roam around an immense system where each wagon was an insignificant anonymous component of an effectively infinite fleet. The NG wagon, on the other hand, was captive in a confined environment and was a much more recognisable member of an intimate family. The AFK therefore uses a different system based upon the probability of a load being offered on a specific day which is determined by using the various dice that have become common in the war gaming hobby. It is nowadays quite easy to obtain dice in 4,6,8,10,12 and 20 sided formats and by combining two 10 sided dice, with one for tens and the other for units, percentage chances can easily be simulated. 100 faced dice are also available but they are more difficult to obtain. In simple terms the dice are thrown and the presence of a load is determined from a table. The AFK uses simple readings taken from the throw of a single dice, rather than adding two values together, for most flows. Adding the values of two dice can create a much more volatile outcome which might be useful in replicating certain traffics and a series of tables is appended at the end of the article to show the effects of combining various dice.
  
  
The dice are the basis of the traffic generating system. These are my original acrylic set although three or four additional sets are available nowadays. The red is the 20 sided, the blue the 12, green 10, purple 8, clear 6 and yellow 4 sided dice. Fantasy war gaming shops usually have a good supply.
  
  
The on layout paperwork for the AFK system is the almost same as that for the 4 cycle system. In the interests of simplicity the AFK uses an envelope with a clear panes to represent each wagon which has the wagon number printed on to it. A pre-prepared note contains details about each load and these are placed inside the pane of the envelope whenever a wagon has been assigned to carry it. The AFK also includes a destination card for each load. For durability this paperwork is printed onto thin card so that it can be reused, and the notes are stored in a set of drawers between sessions. The system is illustrated in Fig 5.1. Each station is equipped with a set of boxes to store the loads and wagons. At the simple wayside sidings one box suffices but the more complex stations are provided with a minimum of three: one each for up and down traffic and one for wagons which will stand unloaded or for loads awaiting forwarding.
  
  
The easiest way to understand the system is to look at the tables created for Boursson (Table 5.1). Examining the pig traffic first, a 10 sided dice is thrown and if it shows a 6 or 7 value then a dozen pigs (one wagon load) will need transport to Lacono slaughterhouse. If the dice shows 8 or 9 then there will be two loads to be taken by the afternoon up goods. The wheat flows are more complex. To initially keep things simple the probabilities outside the harvest season have been shown. The 10 sided dice is set to generate between 0 and 40 tons on any given day and if the dice shows a 2, 3 or 4, for example, 20 tons of wheat need forwarding. On the AFK the tonnage has been tied to the number of axles per wagon, with 10 tons representing one axle. Obviously, a four-wheeled loaded wagon weighing 20 tons would be a rather unlikely animal, especially on the NG, but it provides an easily reckoned loading scheme for goods trains. As there are a number of potential destinations for the wheat, the 10 sided dice is thrown again for each 20 ton load to decide its destination. If it shows 5, for instance, this indicates that there are 20 tons for Eromarbordo (the equivalent of  the down fiddleyard) and a wagon docket is made up accordingly and placed in the down holding box until a stopping goods train can remove it. In this instance, the asterisk shows that this load can only be carried by a bulk grain hopper and other requirements, such as the use of a container, are similarly built into the generating system. If the destination throws showed two 7s then the 40 tons for Lacono could be carried in a bogie van or two four wheelers. This would be an unlikely event for this particular traffic but it is quite common for other flows on the system and the flexibility is often used to provide loads for SG wagons travelling beyond the AFK.
  
  
By the early evening Lacono's yard is full of SG wagons waiting for transport to Relforka so that they can continue their onward journeys.
  
  
This procedure is the basis of the entire traffic system but the odds are manipulated for each commodity and can be varied throughout the year. The AFK’s unspecified year, during the 1960s, initially had five days randomly assigned to each month to fine tune the loads offered and each operating session took place on a specific date (as it still does). This worked well with a smallish layout but as the AFK grew operating sessions lengthened and the current method is to allocate six days (two per month) per season, which speeds up progression throughout the year, although it creates some dislocation requiring manual restaging.(Table 5.2b) Under the older system subtle gradations were incorporated by manipulating the demand on a daily basis, as can be seen for the grain during the harvest season whereas the current system foregoes these nuances. (Table 5.3)  On these occasions the minimum loads are deliberately set at such a level as to overwhelm the normal goods train provision and special trains must be run. These odds, needless to say, can be varied for the same commodity where there are multiple stations, although this would be of less relevance on a simple layout. As an example, the malting barley probabilities at Breĉo de Glissent differ from those at Boursson to represent the contrasting marketing policies of the two Agricultural Co-operatives in these villages and the preferences of the brewers at Karamspur and Bitrano as to which barley varieties they use.
  
  
Despite the labelling the AFK used to use system 5a but it now operates a variation of system 5b which has now been manipulated to give an extra session during April. System 5c would give a quicker progression but would cause more dislocation.
  
  

In the initial stages of establishing the system, it is often difficult to obtain a good balance between the traffic levels and what is required during an operating session. This really is a case of ‘suck it and see’ and it may take a few attempts to strike a balance between the traffic offered, siding space available, stock on hand and the ensuing operational interest. The generator can easily be adjusted by tweaking the dice read outs to provide higher or lower loadings and the system can also accommodate retrospectively added new traffic flows with the minimum of fuss. The AFK tables, needless to say, have had most station pages recalibrated many times. The drawback to using this method on the AFK is the time required to determine the loads and to prepare the consignment notes but on a simple layout the process for inbound and outbound loads should take no more than 5 minutes. The complexity of the current layout mandates an intermediate stage whereby the loads are recorded in water soluble pen on plastic covered paper before the two part consignment notes are assembled. This provides a semi-permanent record available for reference throughout the session should any wagons be accidentally (but prototypically) misdirected and allows the allocation of empty wagons to cover shortfalls. Once the load has been delivered the consignment note is withdrawn and placed in a ‘used’ bin and the wagon is available for another load. Obviously this would not be an instantaneous process and some commonsense has to be used to allow for loading and unloading procedures. At the end of the session the load and destination notes are sorted and replaced in their correct drawers.

The system's advantage is that it allows the level of traffic to vary from day to day and determines whether wagons need to move or whether they will stand in the yard. On a quiet day Boursson may deal with less than half a dozen wagons and yet on another day it may handle 12 or 15. These variations are more apparent when running a single station layout than they are for the whole AFK system because the probabilities tend to balance out across the 16 stations so that a quiet day at one place is matched by an upturn in traffic at another. If there are wagons that remain loaded from the previous day their release into traffic can be determined by another dice throw tied to a table representing a cumulative tapered possibility of their being unloaded, as illustrated in Table 5.4. The relative scarcity of stock on the NG railways made this an unlikely occurrence and we can usually assume that all stock is available for loading at the beginning of the day.
  

The AFK is fortunately large enough that stock can stand out of use on a given day, as was often the case on the prototype. This open stood at Varden throughout an entire session and no movements entered or left the siding. It may be another day or two before it is loaded again.
Some leeway is allowed in meeting traffic demands if vehicles are not immediately on hand, reflecting the priority of different commodities. Certain loads, such as livestock, require urgent attention whereas others, such as cans, can be delayed without serious consequences. Boursson forwards pigs, and also cattle during the winter months, therefore the allocated wagon must be disinfected and have straw placed on the floor. (The AFK does not currently possess special cattle wagons because standard continental NG practice was to provide all the vans with covered openings that could be adjusted to provide ventilation and therefore carry animals.) This procedure takes time therefore suitable wagons cannot be supplied on a casual basis. Farmers must book in advance so that the vans can be prepared and to ensure that staff are on hand to supervise loading. When the dice indicate a cattle or a pig load this equates to an advance booking and a ‘preparation notice’ is placed in the wagon docket. During the afternoon a special consignment note (coloured red) replaces this, ensuring that the load receives immediate attention. Livestock uses the afternoon trains to facilitate loading in the late morning. In actuality, too many afternoon trains were reaching Lacono as ‘engine and van’ so the system was adjusted to generate this traffic.
  
  
Cattle traffic requires that vans are disinfected and have straw placed onto the floor before the cattle are loaded. As has been noted elsewhere the van is a typical continental  NG all purpose van rather than being dedicated to livestock traffic.
  
  

Canned goods, in contrast, are imperishable therefore there is not the need to shift them quite so rapidly. They are an AFK ‘category 2’ load, meaning that the railway can delay providing a wagon until the next day, if necessary. If a wagon cannot be supplied the load is held over until the next session. This does not mean that it conveniently disappears as a consignment note is left in the station boxes for ‘tomorrow’. The priority of loads reflects the rates brokered between the railway company and the consignees thereby reflecting the urgency of the traffic, with most manufactured products being assigned priority 3, that is ‘the day after tomorrow’. The generating day is denoted by a paper clip placed over the relevant day on the load card.

The assumption that all wagons are available for loading implies that there is enough stock on hand, but not too much. One reason for the intermediate stage of recording the loads onto a sheet is the necessity of checking that an appropriate vehicle is available to forward the traffic. Whilst a quick glance at the yard of a simple station will reveal the need for any empties the more complex AFK demands that a (simple) written record is kept of the wagons on hand. This also is written onto a plastic sheet with the water soluble pen for each station showing not only the type and number of vehicles but also their location (such as the canning factory at Boursson). A tick is placed against the loads that can be picked up with whatever vehicles are standing in the station yard and an asterisk is placed against those that need a wagon supplying. Any shortfall on a simple layout is easily resolved by tacking a couple of empties onto the next stopping train as it leaves the fiddleyard or by similarly clearing a clogged yard. One of the subtler challenges of operating even the one station layout is to reduce the movement of empties to a minimum. The AFK downplays the fiddleyard, with the exception of Relforka and Fenditavalat Rivabordo, therefore the empty wagons usually have to be supplied from somewhere else and are transferred using an empties note (coloured blue, or red for an urgent empty, such as one required for the cattle traffic). This process simulates direction from a central office which also attempts to redistribute wagons to pre-empt shortages on the next day. On the AFK congestion is more likely to be a problem, due to the short siding lengths, and wagons are often transferred out to allow flexibility. Lacono and Urteno also serve as mid point reservoirs of spare wagons to avoid too much empty mileage when wagons cannot be transferred from nearby stations.

One by-product of these operating procedures has been the closer management of empties on the AFK. Certain shippers, such as the brewery at Karamspur, provide high levels of traffic and it is obviously sensible to supply plenty of empty vans to meet anticipated demand. Unfortunately, in the early days of the layout, the brewery, and other locations, began to ‘soak up’ vans with severe impacts upon the limited AFK stock forcing a more proactive management system. As a result a pair of evening goods trains was timetabled to transfer surplus empties to Relforka, where they are needed, with the balancing working carrying empty SG wagons on transporters for distribution to those industries which have traffic flows beyond the AFK.
  

The siding beneath the signal box is the store for spare vehicles at the mid point of the AFK. A couple of opens and two or three vans provide a small float of empties that can be taken to wherever needed. The SG vans at the right brought in goods from beyond the AFK yesterday and were then shunted into Lacono's factories and loaded overnight. They will now return to the SG loaded with confectionery.
  
The foregoing paragraph refers to common user vehicles such as vans and opens, which, having arrived at Boursson, are likely find an outward load. Specialised wagons, such as the bulk grain hoppers, have to be returned to their point of origin. On the AFK such flows are as mundane as coal wagons and no arrangements have been made to return these to the colliery at Ithilarak. As coal on the AFK is for industrial use, rather than domestic fuel, it is assumed that the recipients will ensure a quick turnaround of wagons. This might seem unlikely but in Britain the average wayside goods yard was cluttered with coal wagons being used as holding bunkers by small coal merchants. The empties are picked up as and when convenient, unless there is a shortage of wagons at the colliery, in which case efforts are made to speed their return which might require a special trip working up the Vulpafaŭkangulo by the banker. Similar attempts are made to ensure that the SG wagons entering the AFK via Relforka are dealt with as efficiently as possible. The national network begins to charge demurrage at midnight on the third day after delivery, so the AFK keeps track of the wagons on its transporters, endeavouring to return them within the time limit. As far as possible the wagons are reloaded with a consignment of goods going beyond the junction thereby generating some revenue for the AFK instead of being returned empty. A sheet is used to record which SG wagons are on which transporters, their destination, the day that they came onto the AFK and the day that they are due to leave.
  
  
Hopper wagons are regarded as specialised wagons on the AFK and here four stand at Breĉo de Glissent. The white (unfinished) one has been converted from a standard van, as shown by the strapping on its side.
  

Urteno's pilot pulls a trip working of empty coal wagons up the Vulpafaŭkangulo. There is often not enough capacity on scheduled goods trains to return the empties to the colliery necessitating either an extra train or a trip working.
  
To complete these procedures we need to consider the administrative problems of running goods trains. All prototype railways produced loading tables showing how many wagons could be hauled by different locomotive classes over a specific section of line. It was observed earlier that AFK loads are calculated by counting each wagon axle as 10 tons and the locos are classified into four power categories, noted on a loco card, depending what they can haul and what they should be able to haul (Fig 5.2).
  
  
(These latter two are not quite the same thing as, in the tradition of model railways, some of the smaller engines outperform their larger brethren in an unlikely manner!) These classifications were empirically derived as they generated trains that were neither too long for the loops nor too taxing for the locomotives working them over the 1 in 36 gradients. (3) In deference to the gradient the crew van (which contains the hand brake) must be marshalled at the bottom end of the train to prevent breakaways. If desired other wrinkles can be added, courtesy of the American magazines again, such as the prohibition of shunting trains with wooden solebar brake vans between the train and the engine. Many NG railways had similar specific provisions in their rule books.

The result of this pre-prepared paperwork is that each train has an administrative packet that follows it around the layout. The wagon dockets are contained in an envelope that represents the brake van of the train and a timetable card is provided for each train, based on the principles of German working timetables, so that an eye can be kept upon the timings when out on the road (Fig 5.3). The loco card accompanies this packet and the whole is held together with a bulldog clip that fits over pegs that have been inserted into the fascia of the layout, allowing the packet to follow the train’s progress (fig 5.4). Sometimes an additional sheet of notes written in water soluble pen is included when necessary. For a stand alone layout this might be over-egging the pudding as a station timetable extract should suffice, along with a simple load limit.
  

All AFK trains operate within weight limits and that for class I locos on down trains for this section of line is 220 tons which amounts to 5 SG wagons and a NG vehicle. It would be nice to run longer trains but space, as well as feeble model mechanisms prevents this.
  
It could be argued that the procedures outlined in this article are nothing more than an elaborate charade and that ‘off the cuff’ distribution of wagons would suffice to represent a railway going about its business. One could also observe that the arbitrary nature of the values assigned to the traffic probabilities simply distances the ad hoc character by one remove. Railways are, however, transport systems and if we are trying to model them then to my mind we have to attempt a credible simulation of commodity movement between points of origin and destination which this system does despite its limitations. To this end the next article considers the problems that can arise on the real railways.
  
  
1.  The County Donegal, for example, was always short of wagons and Forbes introduced a system whereby lightly loaded wagons had their loads consolidated to ensure more efficient use of stock. He also instigated the conversion of redundant carriages into bogie vans to reduce the vehicles held at customs awaiting clearance. Chapter 11, The County Donegal Companion, R. Crombleholme, Midland Publishing, Hinckley, 2005.

2.  Unusually there is no double ended goods loop here, due to the gradients, therefore wagons for the goods shed need to be at the back of the train. Wagons for the Co-op must be at the front.


3.  Boursson, ironically, has one of the shortest loops on the AFK making it easy to load goods trains beyond the capacity of the loop.
  
Continue to Section 6
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Probabilities