Overbridge, Railway Station, Sea Road, Castlerock, Coleraine, BT51 4TL

Castlerock railway station overbridge is a cast and wrought iron footbridge, almost certainly the structure shown on the Ordnance Survey map of 1904–06 and probably dating from around 1900, though possibly a little earlier. It stands a short distance to the east of the station building, spanning the railway line.

The bridge is constructed from cast and wrought iron components and is reached by a dog-leg stair rising at either side. The guard rails are formed from flat metal strips arranged in a lattice pattern. Treads and walkways are in checker plate, which may be modern overlays over the original surface. The risers are formed from metal plates with geometric piercings. At the foot of each staircase, the entrance is flanked by metal newel posts topped with ball finials. Manufacturer's name plates fixed to the bridge read: "Walter McFarlane & Co., Architectural, Sanitary & Authentic, Ironfounders, Saracen Foundry, Glasgow." This company was founded in 1849–50 and is believed to have supplied similar railway footbridges throughout the world, including at other stations in Ireland. Identical or closely related bridges by McFarlane were erected at Coleraine, Antrim, Ballyclare, Whitehead, York Road and Barn Halt (Carrickfergus) stations, all formerly belonging to the Belfast and Northern Counties Railway. A very similar design was also promoted by George Smith & Company of the Sun Foundry, Glasgow, in the 1890s. The Castlerock bridge is a slightly less ornate version of the design — some examples had particularly decorative balusters — which suggests it may be among the later examples, perhaps around 1900.

The bridge is one of few surviving structures of this type and is considered a good example of wrought and cast iron component construction.

The broader station complex provides important historical context. Castlerock station was originally opened in July 1853 as part of the Londonderry and Coleraine Railway Company's line. The settlement of Castlerock itself grew up partly as a result of the railway company's incentives to build seafront villas in the area. The Belfast and Northern Counties Railway purchased the line in 1871 and rebuilt the station in 1874 to a design by the architect John Lanyon. The original station had been located further east, on the other side of Sea Road; the present station, on the west side of Sea Road, is shown on the Ordnance Survey map of 1904–06 with a footbridge and signal post marked in the same positions as they occupy today.

The station complex as a whole retains several of its principal late 19th and early 20th century components, including the station building, platforms, footbridge and signals. However, the station building has been substantially altered and converted to a public house — probably in the mid to later 1970s — and insufficient historic fabric survives for it to merit separate listing. The platforms have been upgraded, canopies and other ancillary structures have been lost, and the signal box is a modern replacement, though the original control levers have been re-installed inside it.

The somersault-type semaphore signals elsewhere on the site are also of note. Semaphore signalling was introduced to British and Irish railways in the 1850s, but the somersault variant was a specific invention of 1877 by Edward French of the Great Northern Railway in Britain, developed following an accident at Abbots Ripon in 1876 in which the weight of ice on a lower semaphore signal arm prevented it returning to the danger position. The somersault signal avoided this problem because the arm pivots centrally rather than operating in one quadrant. In Ireland, the somersault signal was adopted exclusively by the Belfast and Northern Counties Railway, which introduced them in the late 1880s, though conventional quadrant semaphore signals remained in use alongside them until eventually replaced by colour-light signals. The signal closest to the footbridge consists of the signalling apparatus mounted on a tapering square timber post topped with a metal finial, with a steel access ladder rising to the semaphore arm. Below the arm is a counterbalance weight, which acts as a safety feature: in the event of any system failure, the weight activates the stop command. The mechanism is controlled by a lever and a series of rods running from the signal box, operated manually by the signalman. Three further signals of the same type and construction are positioned along the line into and out of the station.

Much of the railway line on the north coast is single track, and access to single-track sections is still controlled by a token system. Each signalman issues a unique token, staff or key to the driver, and possession of that device gives the driver — and no other — permission to enter the section in question. When the token is removed from its locking mechanism the signal cannot be changed, preventing a second train from entering the section. The driver carries the device through the section and surrenders it to the next signalman, who re-inserts it into the locking mechanism, allowing the signal to be altered again. The return driver then repeats the procedure in reverse. The age of the tokens currently in use is not certain but they appear to be late Victorian in origin. Some sections of the line have since been modernised and are controlled electronically, though the underlying principle of the token system continues in the form of a virtual device that travels electronically with each train.