Pass of Brander stone signals

The railway through the Pass of Brander was opened in July 1880. It was originally part of the Callander and Oban Railway. Since the line's opening, rocks falling from the steep slopes of Ben Cruachan onto the track had threatened to cause a derailment. The secretary of the C&OR, John Anderson, devised a system that would detect falling rocks and provide a warning to drivers. A screen of wires, linked to semaphore signals, would be erected on the mountainside alongside the railway. In the event of one or more wires being broken, signals in each direction would be automatically placed at 'danger'.

The first length of screen was brought into use in January 1882. It was 1,112 yards (1,017 m) in length and there were four associated signals. In April 1883, the screen was extended at both ends, bringing its total length to 5,659 yards (5,175 m). The final extension, at the west end, was made in September 1913, increasing the length to 7,054 yards (6,450 m) - just over four miles (6.5 km).

Signals are erected at intervals of approximately a quarter mile (400 m) along the affected area. There are seventeen signals in all. They are numbered from "1" to "17", with signal 1 being at the east (Dalmally) end. All except number 9 stand on the south side of the line. All the signals apart from numbers 1 and 17 carry two semaphore arms, one for each direction. The signal arms usually all stand in the 'clear' position.

Although trip wires working with colour light signals are occasionally used alongside railways in the vicinity of airports, and are common in railroads running through the Rocky Mountains and similar areas around the world, the remarkable thing about the Pass of Brander system is its age and the fact that it is entirely mechanical in operation.

The system is sometimes referred to as 'Anderson's Piano', after its inventor and the noise that the tensioned screen wires are said to make in the wind.

The system has given early warning of many boulders on the track, but two derailments have occurred where boulders evaded the screen: on 8 August 1946, when the fall occurred just as the train approached, too late for signals to give a warning,[1] and 6 June 2010, when the fall started below the wires.[2] There was an earlier derailment in 1881 before the screen was installed, when a falling boulder hit a train.

• Railway slide fence
• Falls of Cruachan derailment

• http://www.railsigns.uk/info/stonesig1/stonesig1.html details of the signalling
• Stone signals in the Pass of Brander description and photograph
• Thomas, John (1966). The Callander and Oban Railway. Newton Abbot England: David and Charles. p. 83.