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Parliamentary Highland Roads
Scottish Highlands, UK
associated engineer
Thomas Telford
date  1803 -1828
UK era  Georgian  |  category  Road  |  reference  NH515449
ICE reference number  HEW 2538
In the 19th century in the Scottish Highlands, the Highland Roads & Bridges Commission, under the direction of Thomas Telford, was responsible for the building of new roads and the maintenance of earlier military roads. Many of both have since been incorporated into the modern road network, with bitumen-bound surfacing replacing the original water-bound material.
In 1801-3, Thomas Telford (1757-1834) recommended wide-ranging infrastructure improvements in the Highlands. This led in 1803 to Acts of Parliament setting up the Highland Roads & Bridges Commission and the Caledonian Canal Commission. Telford was Engineer to both and directed construction of many roads, ferries and harbours, and the Caledonian Canal (opened 1822) — opening up Scotland to the north and west of the Great Glen.
The existing network of 18th century military roads lay to the east of the Great Glen and the Commission's work involved maintaining and improving them, including the roads to Laggan, Inverfarigaig, Speyside, Argyll, Alford, and Findhorn, and several other shorter stretches.
By the end of 1803, contracts for new roads had been let for several routes, including the 51.5km Glengarry road from Loch Oich to Loch Hourn and the 61km Fort William to Arisaig ‘Road to the Isles’. The 3m wide Glendaruel road, connecting Rothesay on the Isle of Bute with Inveraray, was constructed 1807-12. It was some 30km long, saving 156km on the old post road route, and had a new twin 9.75m span bridge at Ballochindrain (NR995832).
The process of procuring a new piece of infrastructure began with landowners presenting a ‘memorial’ to the commissioners describing the need for a project, and requesting a survey and estimate based on match-funding by the government. If agreed, the survey and estimate were carried out under Telford and, on deposit of the applicants’ share in the Bank of Scotland, details were drawn up and a work contract let.
The roads were generally 3-3.65m wide, though occasionally wider (up to 6.4m). Typically, although not invariably, they consisted of a 150-300mm layer of random-sized local gravel or stones blinded with fine material. Side drains were included. The roads tended to follow the best line available that involved the least cut and fill. Where possible the ruling gradient was usually 1 in 30.
The bridges and culverts needed were built to Telford’s general specification that was published in 1804. It describes the dimensions, foundation requirements, and details of masonry and mortar required. Culverts had spans and heights of 300-760mm, with stone slab soffits. There were four basic types of bridge.
The earliest style of bridge is a hump-backed single span, designed to accommodate a roadway 3.65m wide at the narrowest part. The parapets have an unusual double curvature — a horizontal curve of not less than 910mm in a length of 11m, and a vertical batter of at least 1 in 12 with a concave curve of 100mm. An example is Kinlochmoidart Bridge (NM713720), built around 1815.
The second type is also single span, with near-horizontal coping stones along the parapets, though the double curvature was moderated. An example is Alness Bridge (NN642716) on the Struie Road — formerly the Fearn Road, constructed 1812-7.
The third bridge type has vertical spandrels, battered abutment walls and horizontal coping finished with a quadrant at the ends of the bridge. It was used for longer spans than the previous types. Surviving examples include Easter Fearn Bridge (HEW 322, NH641863) on the Struie Road, and Shiel Bridge (HEW 614, NG939188) on the Genshiel Road, completed 1817.
The fourth type is larger still — often multi-span, with dressed masonry and cutwaters. They were designed for specific locations, often let as separate contracts, and many are still in use. The largest is the 209m Dunkeld Bridge (HEW 149, NO027425), built 1804-8, which cost “above £30,000” and carried the A9 until a new bridge opened in 1977. It has seven arches with hollow spandrels.
Other examples of multi-span bridges include the 1811-4 Potarch Bridge (HEW 1382, NO608973), at Kincardine o’Neil, on the route of the military road between Edinburgh and Fort George, which carries the B993 over the River Dee. Bonar Bridge (HEW 2550, NH609915) and Craigellachie Bridge (HEW 24, NJ285452), built 1812-4, had innovative prefabricated cast iron lattice spandrels on the main arch — though only Craigellachie survives, Bonar was destroyed by a flood in January 1892. Spean Bridge (NN222817), completed 1815, has asymmetrical side arches and is on the longest road east of the Great Glen — the 68km Laggan Road, now the A9, built 1810-8.
Construction was superintended by John Mitchell (1779-1824), described by Telford as “a man of inflexible integrity, a fearless temper and indefatigable frame” whose gruelling workload undoubtedly contributed to his early death aged 45. He presided over a group of inspectors, one for each district.
The commissioners’ epoch-making work was wound up in 1821, and construction of new roads stopped in 1828. They pointed out with pride that they had found the country “barren and uncultivated … and inhabited by poor and ill-employed peasantry” and had left it with “a profitable agriculture, a thriving population, and an active industry”.
Telford reported that in 1828 there were 1,117 bridges (with a total of 1,202 arches) and 1,931km of road — including 450km of military roads under maintenance. The average cost of the roads was under £250 per km, with annual maintenance expenses of about £3.80 per km. The work was completed in 120 separate contracts.
This process of improvement, mainly maintenance, continued under the remit of the Repair Commission until it too was wound up, in 1863. After 1824 until the early 1830s, work was carried out under the superintendence of Joseph Mitchell (1803-83), son of John Mitchell, under Telford’s general direction. Mitchell afterwards assumed the role of Engineer, which included remedying the damage to the roads and at least 10 of the larger bridges built by Telford caused by the Great Moray Floods of 1829.
Chief inspector (1804-24): John Mitchell
Chief inspector (1824-30s): Joseph Mitchell
District inspectors: Robert Garrow (Argyllshire), George Macfarlane (Badenoch), Thomas Spence (Caithness & Sutherland), Daniel McInnes (Lochaber), John Pollock (Lowland), Robert Murray (Ross-shire), James Smith (Skye)
Research: ECPK
"Highland Roads and Bridges" by Thomas Telford, in Life of Telford, Vol.1, pp.162-171, ICE virtual library, London, January 1838
"Military Roads, Road Repair" by Thomas Telford, in Life of Telford, Vol.1, pp.173-178, ICE virtual library, London, January 1838
"The Public Works of Thomas Telford", microfilm collection edited by Alastair Penfold, Microform Limited, Wakefield, 1970
"Roads and bridges in the Scottish Highlands: the Route between Dunkeld and Inverness, 1725-1925" by G.R. Curtis, in Proceedings of the Society of Antiquaries of Scotland, Vol.110 (1978-80), pp.475-496
reference sources   CEH SHICEH SLBBDCE1

Parliamentary Highland Roads