The gauge of 4ft. 8 ½in. was selected for the pioneer railways by George Stephenson and his associates. This measurement was the distance between the centres of the ancient Roman stoneways, traces of which still exist, and also the distance between the wheels of the old coal wagons that carried the produce of the North of England mines. One English railway, however—the Great Western—departed from the conventional gauge of 4ft. 8 ½in. Isambard Brunel was the engineer of this system, and he was a firm believer in a wide gauge that would permit of the employment of roomier carriages and locomotives with boilers pitched well down between the wheels. In its own way, the 7ft. gauge of the Great Western possessed many advantages. Unfortunately, the position of the Great Western in time became untenable, as it was an impossibility to operate through trains or vehicles between its system and neighbouring lines. To get over the difficulty, Brunel laid a third running rail between the two broad gauge rails, so that trains of either 7ft. or 4ft. 8 ½in. could be handled. This, however, was only a temporary measure. Lengthy sections of track were by degrees converted to the Home railway standard gauge of 4ft. 8 ½in., the last stretch to be altered being that between Exeter and Penzance.

Railways in many parts of the globe today are built to the 4ft. 8 ½in. gauge, 67 per cent. of the world's railways being so constructed. The metre gauge is the second most favoured dimension, representing 10 per cent. of the world's railway trackage. The 3ft. 6in. gauge, as employed in New Zealand, South Africa, Japan, Queensland, Western and South Australia, comes third on the list of most popular gauges. Below 3ft. 6in. there are railways in different parts of the globe built to all gauges, down to as low as 1ft. 3in. Among toy public railways of tiny gauge are the famous Ravenglass and Eskdale; and Romney, Hythe and Dymchurch systems, that come as a constant joy to every overseas railway visitor to the Homeland.