Stephenson's Tubular Bridge, Conwy

Link to French translationbutton_lang_japaneseStephenson’s Tubular Bridge, Conwy

Painting of tubular bridge construction
© Science Museum / Science & Society Picture Library

The railway tracks past Conwy Castle disappear into two iron “tunnels” which are also a bridge over the estuary. This was a pioneering design by renowned engineer Robert Stephenson (1803-59), although he depended on the help of others including Isambard Kingdom Brunel and William Fairbairn.

They worked out that to support a train, the big tubes would need reinforcement by rows of small tubes, along the top and bottom. This makes the bridge at Conwy the ancestor of countless “box girder” bridges worldwide.

The tubes were constructed on the shore, floated into position on pontoons and – with numerous setbacks – jacked up to the correct height. The painting, shown here by kind permission of the Science & Society Picture Library/Science Museum, shows the second tube ready for lifting.

Stephenson himself rode the first locomotive to cross, on 18 April 1848. The first tube opened to traffic on 1 May that year. The second tube was placed in position in January 1849.

Photo of train at tubular bridge
© National Railway Museum /
Science & Society Picture Library

Supporting piers were added, one each side of the estuary channel, in 1899. The trains enter the tubes through tall masonry portals, designed to complement the adjacent castle. The photo on the left, courtesy of the SSPL/NRM, shows a Holyhead-bound express emerging from the bridge, probably in the 1930s.

The full span of the tubes is best seen from the south, near the bowling green off Llanrwst Road. The bridge is now owned and maintained by Network Rail.

Stephenson built three other bridges with the same principles, including a very long one in Canada, but only Conwy survives as a tubular bridge. The photo on the right shows a cross-section through a tube from his Britannia Bridge, near Bangor. Brunel adapted the tubular principle for his rail bridge at Chepstow.

Also in this vicinity is a goods crane constructed by the London & North Western Railway at Crewe. The railway occupied a wide ledge built out over the north bank of the Gyffin river. Between the main lines and the town walls was a yard and goods shed, where freight was loaded or unloaded.bangor_britannia_bridge_cross_section

FOOTNOTES: More about Stephenson’s tubular bridges

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Other RAILWAY HiPoints in this area:
Conwy railway arch
Llandudno Junction station – unusually the town is named after its station

Website of Science & Society Picture Library - prints available of the above images and many others