Kylesku Bridge

Coordinates: 58°15′26″N 5°01′26″W / 58.257318°N 5.023792°W / 58.257318; -5.023792
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Kylesku Bridge

Drochaid a' Chaolais Chumhaing
Coordinates58°15′26″N 5°01′26″W / 58.257318°N 5.023792°W / 58.257318; -5.023792
grid reference NC233330
CarriesA894, one footway
CrossesLoch a' Chàirn Bhàin (Caolas Cumhann)
DesignPrestressed box girder
Total length276 m (906 ft)
Longest span79 m (259 ft)
No. of spans5
Clearance below24 m (79 ft)
Engineering design byOve Arup
Construction startAugust 1982
Construction cost£4 million
OpenedJuly 1984
Inaugurated8 August 1984
ReplacesKylesku and Kylestrome ferry

The Kylesku Bridge (officially known since 2019 by its Gaelic name Drochaid a' Chaolais Chumhaing[1]) is a distinctively curved concrete box girder bridge in north-west Scotland that crosses the Loch a' Chàirn Bhàin in Sutherland. It is listed as category A, the highest grade.


In June 1978, the Highland Regional Council asked Ove Arup & Partners Scotland to prepare a feasibility study for a bridge, in their capacity as consulting civil engineers, and it was prepared by March 1979.[2]

Construction for the approach roads, costing £4 million, began in summer 1981. Construction of the bridge began in August 1982, with Morrison Construction and Lehane, Mackenzie and Shand the chief contractors.[2]

It was constructed by building out the supporting legs and then lifting into place the central span, which weighed 640 tonnes (630 long tons; 710 short tons).[3][4]

The cost of the bridge was £4 million, although was earlier budgeted at £2.75 million. The bridge opened to traffic in July 1984, and was formally opened by the Queen on 8 August 1984.[2]

In 2019, the bridge was classified by Historic Environment Scotland as a Category A structure, recognising it as "visually striking and technically innovative". It was also officially renamed to the Gaelic translation of its name, Drochaid a' Chaolais Chumhaing.[1]


The bridge crosses water which is approximately 120 metres (390 ft) wide and up to 25 metres (82 ft) deep, leading to fast tidal currents.[2] It replaced the ferry between Kylesku and Kylestrome, which was approximately 400 metres (1,300 ft) to the east.


The bridge is 275 metres (902 ft) long with a 79-metre (259 ft) long main span. The bridge deck is at a height of 24 metres (79 ft) above high water to provide navigation for ships.[2]

The bridge deck is supported by V-shaped inclined piers, with eight inclined legs, in order to reduce the length of the main span.[2] The lateral forces from each leg balance, so the total force on the foundations is vertically downwards.[2] The spread of legs supports the bridge in winds which can exceed 100 miles per hour (160 km/h), and also loads resulting from the curvature of the bridge.[4][2] There is no joint between the legs and the deck of the bridge, with the expansion joints and bearings being located at the abutments to facilitate straightforward maintenance.[4] The legs are formed from reinforced concrete and the deck from prestressed concrete using cables tensioned at up to 52,200 kN.[2]

The bridge is designed to be sympathetic to the surrounding country, and the approaches were chosen to minimise changes to the landscape.[2]


  1. ^ a b "Kylesku Bridge given A-list status and legal Gaelic renaming". Retrieved 16 February 2019.
  2. ^ a b c d e f g h i j Stears, H.S. (January 1985). "The Kylesku Bridge - Design and Construction". The Journal of the Institution of Highways and Transportation & HTTA. 32 (1): 16–20.
  3. ^ "D-block GB-220000-933000 Bridge Building at Kylesku". Retrieved 3 February 2015.
  4. ^ a b c Martin, J. M. (1986). "The Construction of Kylesku Bridge". ICE Proceedings. 80 (2): 317. doi:10.1680/iicep.1986.737.

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