The railway was carried mainly on iron viaducts, with a corrugated iron decking onto which the tracks were laid. It was vulnerable to corrosion, especially as the steam-operated Docks Railway operated beneath some sections, despite the locomotives being fitted with chimney cowls which were intended to deflect the steam from the structure. Parts of the decking had become rusty on the surface, caused by steam and soot from the dock locomotives that passed underneath, mixing with rainwater to form an acid that began to corrode the metalwork. Drainage blockages combined with grit and constant vibration also played a part in the degradation of the structure.