“Earlier, what was being envisaged included extension of the existing minor bridges so as to accommodate the new DFC line. That would have lengthened the overall period of construction and also forced speed restrictions on existing lines. Taking this aspect into consideration we are now going away from the existing alignment as much as possible to ensure there is no ripple effect on the existing lines,” Kaul added, saying that route alignments spread over 300 km had already been frozen and the rest was likely to be frozen in 3-4 months. DFCCIL has further pointed out that for operational reasons, all existing level crossings would need to be replaced by Road Over Bridges (ROBs). For this, as many as 906 ROBs, 529 on the Western Corridor and 377 on the Eastern Corridor, would need to be constructed and that would involve about 28 per cent of the total cost of the project. In addition, the existing ROBs would need to be rebuild so as to increase their height by 2.2 metres to provide extra clearance area for double or triple stacked trains.