<P> Narrow - gauge railways usually cost less to build because they are usually lighter in construction , using smaller cars and locomotives ( smaller loading gauge ) , as well as smaller bridges , smaller tunnels ( smaller structure gauge ) and tighter curves . Narrow gauge is thus often used in mountainous terrain , where the savings in civil engineering work can be substantial . It is also used in sparsely populated areas where the potential demand is too low for broader gauge railways to be economically viable . This is the case in some of Australia and most of Southern Africa , where extremely poor soils have led to population densities too low for standard gauge to be viable . </P>
<P> Narrow - gauge railways usually cost less to build because they are usually lighter in construction , using smaller cars and locomotives ( smaller loading gauge ) , as well as smaller bridges , smaller tunnels ( smaller structure gauge ) and tighter curves . Narrow gauge is thus often used in mountainous terrain , where the savings in civil engineering work can be substantial . It is also used in sparsely populated areas where the potential demand is too low for broader gauge railways to be economically viable . This is the case in some of Australia and most of Southern Africa , where extremely poor soils have led to population densities too low for standard gauge to be viable . </P>
which of the gauges is used by railway in the hilly areas
which of the gauges is used by railway in the hilly areas
Narrow gauge
Narrow gauge