Meldon Viaduct is a truss bridge, spanning the West Okement River, located near Okehampton, at Meldon, Devon.
In the 19th century, the London & South Western Railway - LSWR was in competition with the Great Western Railway - GWR to provide passenger trains from London to Devon and Cornwall. But as the South Devon Railway, an associate of the GWR, had already built a line from Exeter St Davids to Plymouth along the south coast, designed by Isambard Kingdom Brunel. The LSWR, and its engineer, William Galbraith, were only left with a route that would have to cross the uplands of Dartmoor.
Work began on Meldon Viaduct in 1871 and was completed in 1874, it was part of the LSWR's route to Plymouth and Bude via Okehampton. The Victorian ironwork of the viaduct shows the gentle curve it makes as it spans the 165 m , 541 ft gorge. Originally it carried a single track, part of the Exeter to Plymouth railway of the LSWR, but the track was doubled in 1878 when a steel viaduct of similar design was constructed by interconnecting the structure. This was completed while the original line remained open.
No high scaffolding was used, the trestles were erected by means of derricks mounted on the original structure. The trusses were constructed in a railway siding and lifted by means of two heavily-ballasted, rail-mounted cranes that were then pushed onto the original bridge and swung out into position by the cranes. Each truss could be thus installed within around two hours and thirty minutes, meaning that the work could be arranged around the railway timetable to avoid the need to close the line at any stage. The method, devised by engineer T Wrightson and supervised on site by W Jacomb, worked well and the new bridge was complete within 16 weeks of starting work.
The speed limit was set at 20 miles per hour in 1927. The trestles were strengthened in 1938 and 1944 in order to allow heavier traffic to use the viaduct during the Second World War, and further strengthening to the trestles was carried out in 1959 and 1960. On 5 May 1931 a carpenter, F. Rook, was killed in an accident whilst replacing timber decking on the down line.
Passenger services on the line were withdrawn in 1968, after which the line reverted to a single track and the viaduct was used predominantly for shunting freight trains serving the ballast quarry at Meldon. In 1970, a road was built across the viaduct to permit lorries access to the Meldon Dam construction site.
The bridge was assessed in 1990 as being too weak to carry trains and the rails were removed. Six years later, the viaduct was refurbished and re-opened as part of The Granite Way, a long-distance cycle track across Dartmoor. The viaduct, which is a scheduled monument, is now one of only two such surviving railway bridges in the United Kingdom that uses wrought iron lattice piers to support the cast iron trusses, the other is the Bennerley Viaduct between Nottinghamshire and Derbyshire.
The viaduct is now owned by the Meldon Viaduct Company, a not-for-profit organisation set up in February 1999 to safeguard the viaduct.
At various times since the closure of the line, local people and enthusiasts have campaigned for its re-opening, a campaign which gained added prominence in 2014 after severe winter storms severed the Great Western Main Line at Dawlish in February. According to Network Rail, the condition of Meldon Viaduct was a significant obstacle to the re-opening of the line and it would need to be replaced before trains could run on the line