 In 1839 the railway was upgraded to standard gauge with heavier rails, and gradients on the main line improved.The main line of the railway followed the route towards Johnstone shown in John Thomson's "Atlas of Scotland".From Ardrossan, the proposed line goes east through Saltcoats then to the south of Stevenston before turning north between Dubbs and Todhills to pass to the west of Kilwinning, where the railway terminated.