Caledonian Canal Swing Bridges
| Caledonian Canal Swing Bridges | |||
| |||
| Location | |||
| Great Glen | |||
| County | |||
| Argyll • Inverness-shire | |||
| Additional Information | |||
| |||
| On road(s) | |||
| A82 • A830 • A862 • B8004 | |||
The Caledonian Canal follows the Great Glen from Fort William in the south to Inverness in the north. Whilst the canal is well out of the scope of this website, the 7 road bridges along its length are definitely of interest, and are described below.
The Bridges
The A82 crosses the canal no less than 4 times between Fort William and Inverness, with another three bridges carrying (from North to South) the A830, B8004 and A862. Of all of these, only the B8004 bridge varies from the standard design.
The first bridge found on the voyage from Fort William northwards carries the A830 across the canal at Banavie on the edge of Fort William. Immediately to the west, the B8004 turns off to follow the canal north up to Gairlochy (See below), while to the east, the B8006 follows south towards the canal entrance at Corpach Basin. To the north of the bridge, the famous Neptunes Staircase of locks lift the canal up to nearly the level of Loch Lochy, about 7 miles to the north.
The original bridge across the canal at Banavie was further north, across the third lock. The road was initially realigned alongside the canal to use the current bridge site in the 1930s, with the eastern approach completely realigned across the Blar Mhor in the 1970s. The bridge was replaced again at the same time.
The bridge swings on the east bank, the separate control cabin, which also controls the adjacent railway bridge, is at the north east corner of the road bridge.
Gairlochy
The B8004 is carried across the canal at Gairlochy on a unique bridge. Single Carriageway, and missing the large control cabin, the bridge at Gairlochy seems very low-tech compared to the others!
The bridge swings on the west bank, the control 'cupboard' is on the north side of the bridge.
A couple of miles to the south of Gairlochy is the only bridge that survives from the original structures designed by Thomas Telford in the 1820s. It is a two-part lifting bridge, which requires the bridge keeper to row across the canal in order to hand crank the opposite side!
Laggan
The A82 is carried across the canal at Laggan at the southern end of Loch Oich.
The bridge swings on the west bank, with the cabin on the north side.
Aberchalder
The A82 is carried across the canal between the Bridge of Oich and Aberchalder at the northern end of Loch Oich. Immediately to the north of the bridge, the foundations of the original swing bridge can still be seen at the side of the canal.
The bridge swings on the east bank, with the cabin on the south side.
Fort Augustus
The A82 is again carried across the canal at Fort Augustus at the southern end of Loch Ness. Immediately south of the road, and bisecting this small village, a series of locks carry the canal up the hill to the level of Loch Oich, nearly 6 miles to the south.
The bridge swings on the east bank, with the cabin on the 'north' side.
Inverness - Tomnahurich
The A82 enters Inverness proper by crossing the canal at Tomnahurich on the south side of the city. Originally there was a single bridge here, but in order to avoid delays a second bridge has been added as part of the Inverness Westlink, forming a triangular Magic Gyratory with roundabouts at each corner. The original bridge has a control cabin on the south side of the A82 adjacent to the west end of the bridge. With the new bridge coming into use in 2021, both bridges are worked from a "control tower" located between the bridges. This allows one bridge to be opened at a time, with A82 traffic using the other bridge. Both bridges swing on the west bank. No name has been announced for the new bridge, so it appears the the Tomnahurich name now applies to both.
Inverness - Muirtown
The A862 (former A9) is carried across the canal next to the Muirtown Basin on the west side of Inverness.
The bridge swings on the west bank, with the cabin on the north side.
Design
All of the bridges are full S2 (except Gairlochy), and were installed between 1930 and 1935 to replace old single-track bridges. Most of them rotate on the eastern bank, with the control cabin being on the bridge structure. However, the bridge at Banavie (on the A830) has the cabin as a fixed building on the eastern bank. This is due to the close proximity of the Railway swing bridge. Also, the two bridges in Inverness swing on the southern/western bank.
The structures themselves are metal, presumably steel or iron, and trough shaped, with substantial depth to the decks to carry the weight of the traffic. When they are open, the bridges 'rest' on latticed concrete structures set on the bank of the canal.
Operation
The bridges are still operated locally, from the control cabin at the side of the bridge. The road is closed by both gates and wig-wag signs. The first operation to open the bridge is to lift it slightly, off of the base to allow it to swing. It then rotates (frustratingly slowly), a full 90 degrees to clear the canal. When shutting, the final operation is to lower the bridge and lock it back into position.
Depending on the volume of boats wishing to pass, the bridge can be open for nearly ten minutes, or hardly stop between the open and close manouveres if there is just a single small craft wishing to pass. For health and safety reasons, only canoes and other small craft are allowed to pass under the bridge whilst it is open to traffic.
History
The original bridges over the Canal were a mixture of lifting and swing bridges, all hand cranked. The only surviving example is that at Moy Bridge on the Fort William - Gairlochy stretch of the canal, although this has never carried a public road! Further north, the foundations of the old bridge can still be seen just to the north of the Laggan Bridge.
