The choice of gauge is very limited, as each country has a fixed gauge and all new railway lines are constructed to adhere to the standard gauge. However, the following factors theoretically influence the choice of the gauge.
There is only a marginal increase in the cost of the track if a wider gauge is adopted. In this connection, the following points are important.
(a) There is a proportional increase in the cost of acquisition of land, earthwork, rails, sleepers, ballast, and other track items when constructing a wider gauge.
(b) The cost of building bridges, culverts, and tunnels increases only marginally due to a wider gauge.
(c) The cost of constructing station buildings, platforms, staff quarters, level crossings, signals, etc. associated with the railway network is more or less the same for all gauges.
(d) The cost of rolling stock is independent of the gauge of the track for carrying the same volume of traffic.
The volume of traffic depends upon the size of wagons and the speed and hauling capacity of the train.
(a) As a wider gauge can carry larger wagons and coaches, it can theoretically carry more traffic.
(b) A wider gauge has a greater potential at higher speeds, because speed is a function of the diameter of the wheel, which in turn is limited by the width of the gauge.
(c) The type of traction and signalling equipment required are independent of the gauge.
Physical Features of the Country
It is possible to adopt steeper gradients and sharper curves for a narrow gauge as compared to a wider gauge.
Uniformity of Gauge
The existence of a uniform gauge in a country enables smooth, speedy, and efficient operation of trains. Therefore a single gauge should be adopted irrespective of the minor advantages of a wider gauge and the few limitations of a narrower gauge.