Narrow Gauge

India has a substantial narrow-gauge network, most of which uses the 1 m (3 ft 33⁄8 in) gauge. There are some lines that use a 2 ft 6 in (762 mm) gauge, and a few that use 2 ft (610 mm) gauge. These are what are known in India as "narrow gauge" (as opposed to "metre gauge") lines. About 17,000 km of route are metre-gauge in India.

In 1999 the Darjeeling Himalayan Railway (sometimes called the Darjeeling "Toy Train") was officially designated as a UNESCO World Heritage Site. It is a 2 ft (610 mm) gauge narrow-gauge railway that runs from Siliguri to Darjeeling in the state of West Bengal in India. The railway travels through spectacular mountain scenery and uses several unusual civil engineering techniques to gain the necessary height including several switchbacks, and spirals including the famous double loop at Agony Point. The line was inspired by the earlier success of the 1 ft 111⁄2 in (597 mm) gauge Ffestiniog Railway in North Wales. Until recently all trains on the railway were powered by steam locomotives; however in 2001 two modern diesel engines were built for the line and now most trains are diesel hauled.

Advantages of narrow gauge

Narrow-gauge railways cost less to build because they are lighter in construction, using smaller cars and locomotives as well as smaller bridges, smaller tunnels and tighter curves. Narrow gauge is thus often used in mountainous terrain, where the savings in heavy civil engineering work can be substantial. It is also used in very sparsely populated areas where the potential demand is too low for the building of broader gauge railways to be economically viable. This is the case in most of Australia and Southern Africa, where extremely old soils can support only population densities too low for standard gauge to be viable.

Disadvantages of the narrow gauge

Narrow gauge railroads generally cannot interchange equipment, particularly freight and passenger cars, with the standard gauge railroads they link with, unless they use variable gauge axles. The means that narrow-gauge lines have a built-in cost of transshipping people and freight to the mainline railway system. The cost of transshipment is a substantial drain on the finances of a small railroad because it involves expensive and time consuming manual labor or substantial capital expenditures. Some bulk commodities, such as coal, ore and gravel, can be mechanically transshipped, but this still incurs time penalties and these mechanical devices are often complex to maintain.