 However, the poorly-patronized branch line between Dum Dum Cantonment railway station and Biman Bandar railway station is replaced by Line 4 (under construction) of the Kolkata Metro, which follows the same route.With the population of the Kolkata metropolis continuing to grow, and road transport being unable to cope with demand due to bottlenecks on the roads, it was felt necessary to introduce an additional method of transportation which would ease the congestion problem particularly at peak hours.Of the various modes considered, including tramcars and buses, the railway was found to be most suitable.