After the First World War, another programme of improvements to the locks was carried out, extending the locks to , which enabled trains of 19 compartments to operate regularly. Experiments with trains as long as 38 tubs were carried out, but the difficulty of splitting the train to pass through the locks meant that 19 was the usual maximum. The compartments continued until the late 1960s to carry around half a million tons of coal, long after most British canals had ceased to be used for commercial traffic, but the gradual demise of the coal industry led to compartment traffic ceasing in 1986.