The Nilgiri Mountain railway starts from the town of Mettupalayam and thus begins a journey full of twists and turns, as this narrow gauge train ascends 46-km., on its way to the hill resort of Ooty. At a maximum speed of 33-km per hour, this 'toy train' treks across plains, plantations and forest clad hills. The 16 tunnels and tall girder bridges on the way, along with the breathtaking view, make this toy train journey to Ooty, something not to be missed.
This Nilgiri rail system is unique as it is the steepest one in Asia. In combination with this gradient there are many curves. To overcome this incline the Nilgiri Railway uses a unique `rack and pinion' rail system. In this system, between the two conventional rails, there are two rack bars, out of step with each other, on which the pinions of the locos and coaches 'climb' in a similar manner as a person climbing a ladder using his feet alternately.
Presently all traffic on the rack section is ably handled by the eight X class locomotives built by SLM of Switzerland. These locomotives have four cylinders instead of the conventional two. The main cylinders of the locomotive use high-pressure steam and drive the wheels of the loco while the smaller cylinders using low-pressure steam drive the rack system of the Nilgiri Railway system. Another interesting thing associated with the Nilgiri Railway is that the youngest X class loco is over 50 years old and the oldest is 80 years old!