This system uses hopper wagons which carry around 914 tonnes of coal each.

Other wagon types included flat wagons, vans, tarpaulin wagons, tank and hopper wagons, as well as three cranes.

Following the trial, National Power ordered a further five locomotives and a fleet of hopper wagons to carry coal and limestone.

Unlike normal hopper wagons, however, their discharge cannot be controlled and the entire load must be dropped.

One example is the large coal-fired power station in Mannheim where coal is delivered by rail in long trains of self-discharging hopper wagons.

Today, however, most coal and aggregates are moved in hopper wagons that can be filled and discharged rapidly, to enable efficient handling of the materials.

Two four-wheeled hopper wagons, builder unknown, ex La Mine Orne.

One four-wheeled hopper wagon, ex SNCF, standard gauge.

As a general rule, a hopper wagon involves an open frame with sloped sheets, giving a wider area at the top and a smaller area at the bottom.

Three trains of twenty hopper wagons each were made up, with a Class WT locomotive at each end.