 The Cogan Viaduct ( Welsh : Traphont Cogan ) is the most important element of the Cogan Spur as it crosses the River Ely with a central span of 95 metres ( 312 ft ) . In total it has 6 spans ; 40 m ( 130 ft ) , 60 m ( 200 ft ) , 60 m , <unk> , 95 m and 60 m . It is made from a multi @-@ span glued segmental structure of rectangular box sections . In all over 300 sections were used to construct the viaduct , each weighing from 43 to 117 tonnes . The Cogan Viaduct was again designed by South Glamorgan County Council , who won a Concrete Society Commendation in 1989 for the design . 
