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Although Northern Ireland remains part of the United Kingdom, its railways are run entirely separately from those in Great Britain. After the partitioning of Ireland in 1921, the British railway inspectorate ceased to operate in either part of the island. Northern Ireland Railways has chosen to continue following the practices of Great Britain, but it is not obliged to do so. Signalling and signage in Northern Ireland can therefore generally be considered as a subset of that in Great Britain.
Mechanical signalling is on the verge of extinction in Northern Ireland. Upper quadrant semaphore signals had once existed at Larne Harbour and on the Bangor line, but the few surviving semaphore signals in Northern Ireland (at Portrush) are all of the 'somersault' type (see [2.36]).
Older permanent speed restriction signs were of the 'cut-out' type, additionally surmounted by a cut-out letter "C" for 'commencement' [NI.1]. The terminating point of the speed restriction was correspondingly marked by a cut-out letter "T" [NI.2].
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| [NI.1] Permanent Speed Restriction Sign. | [NI.2] End of Permanent Speed Restriction Marker. |
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In what is a significant departure from the usual British practice, modern speed restriction signs in Northern Ireland, both permanent and temporary, are of the same types as those found in the Republic of Ireland (see [IE.18] and [IE.23 - IE.27]). However, permanent speed restriction signs applicable to diverging routes are fitted with a standard matching design of directional arrow positioned below the board [NI.3]. |
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In common with current practice in Great Britain, a warning indicator may be installed on the approach to a severe reduction in permissible speed [NI.4]. |
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Some early whistle signs remain, which comprise a cut-out letter "W" [NI.5]. The more recent whistle boards are of the same circular pattern that is standard in Great Britain (see [15.6]). |
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'Distant monitored' level crossings are unique to Northern Ireland. These were either open or had half barriers, being termed "Automatic Open Crossing, Distant Monitored" (AOCD) and "Automatic Half Barrier Crossing, Distant Monitored" (AHBD), respectively. Both appear alike from the point of view of the train driver, and in some respects they are similar to an "Automatic Open Crossing, Locally Monitored" (AOCL). The driver's white light (see [16.13]) is, however, located some distance before reaching the crossing, and it may be co-located with the crossing speed restriction sign (see [16.26]). This is too far away for the driver to be able to ascertain whether the crossing is clear of obstructions. The crossing is therefore 'distant monitored' from a signal box, where the signalman has the facility to extinguish the driver's white light in an emergency. Higher crossing speeds were permitted at AOCDs than is the case at AOCLs. The advance warning board for a distant monitored crossing has a black St. Andrew's cross on a white background [NI.6] instead of the usual St. George's cross (see [16.15]). No AOCD (or AOCL) level crossings remain in Northern Ireland, but there are three AHBDs at Cullybackey. |
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Marker boards may be installed on either side of a user-worked level crossing to enable engineering staff to check that sighting distances for crossing users have not been compromised by vegetation growth. These comprise an upright rectangular board divided diagonally into black and white sections [NI.7]. |
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Radio channel indicators are similar to the type that was standard in Great Britain (see [19.15 - 19.17]), but they have the letters "RAD CH" (for 'radio channel') at the top [NI.8 & NI.9]. The radio channel indicators originally installed [NI.8] were much larger and wider than the later style [NI.9].
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| [NI.8] Radio Channel Indicator. | [NI.9] Radio Channel Indicator. |
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