2020.02.20 Cambrian goods traffic
Though the Working Timetable gives schedules for goods trains, it says little or nothing about what those trains carry, or the origin or destination of individual loads. There are two main aspects to this: what traffic is handled by each station, and ideally by each siding, and how trains are put together or broken down in the main yards, affected by the main traffic flows.
To take Ynyslas as an example, we have only two sidings. There is the H Jones timber yard south of the station on the stub of the former ferry branch, dealing only with timber traffic, and a single siding adjacent to the station, with access over a crossing to avoid a facing point. Photos show that this single siding served general and coal traffic and also had a small cattle pen; it could be shunted conveniently only by a northbound train. The timber siding was further from the station, too far for the point to be worked from the signal box. instead, a southbound working would leave most of its train in the station, pick up the key from the signalbox, and proceed to shunt the siding, then returning the key and picking up the train.
The other aspect of freight handling results from the fact that goods traffic in the fifties was still mainly handled in individual wagon loads. In most cases a wagon would need to be shunted from one train to another several times before reaching its destination. So when creating representative shunting tasks for a simulation, we have to assess the likely traffic flows. In the case of Cambrian Railways, it is clear that most traffic would follow the main line to or from Oswestry or Shrewsbury, and thence serve yards all over the country. There are some exceptions, though. The line serving Brecon from Moat Lane Junction probably fed into "main line" trains in both directions. It is well documented that during the First World War this line was heavily used for the "Jellicoe Specials", coal trains to Scotland with fuel for the Royal Navy, and it seems likely that this line would have taken a share of the traffic between South Wales and the Cambrian stations, along with the routes via Carmarthen and Shrewsbury.
Nowhere on the Cambrian system had a sizeable marshalling yard, so the remarshalling of goods traffic would be limited to splitting and joining of portions at the main stations: Oswestry, Welshpool, Newtown, Moat Lane Junction and Machynlleth. In marked contrast say to our Shrewsbury simulation, there are seldom more than 2 or 3 possible departures for an arrival to connect with.
To take an example of originating traffic, let's look at the quarries in the Porth-y-Waen area. These generate a number of traffics, particularly lime for agriculture and other uses, granite for building and for ballast, and limestone for various industrial uses. Much of the traffic goes to Oswestry to connect with departures on all routes, but some, particularly ballast, is transferred to westbound services at Llynclys Junction.