The construction of a new railway line in an area is normally required for one or more of the following reasons.
(a) Strategic and political considerations
(b) Development of backward areas
(c) Connecting new trade centres
(d) Shortening existing rail lines
Existing single railway lines are also doubled in a few cases to cope with the burden of additional traffic. Recently, a large number of projects have been undertaken for converting existing metre gauge lines into broad gauge lines in order to ensure a uniform gauge for the smooth flow of traffic.