The New Zealand Railways Magazine, Volume 2, Issue 4 (August 1, 1927)
Does double-heading pay? This is a question which many Home locomotive and operating officers are at present asking. The desirability or otherwise of employing a couple of engines for hauling a heavily-laden passenger train, rather than running the train in two portions, or introducing a more powerful type of locomotive, is a question of much controversy. page 21 When two engines are employed for train haulage, danger and discomfort to passengers not infrequently arise through lack of unison between the drivers. Here, in England, many trains may be observed drawn by two engines of the same class: this would, in the majority of cases, appear an unnecessary waste of power. An assisting engine is usually called for when the load is just too much for the train engine to handle independently, and the assistance demanded is not, as a general rule, such as to necessitate an extra engine of equal power to that of the train locomotive. With the introduction of more powerful locomotive types, double-headed trains are on the decline at Home, yet the problem still remains on many routes.