The track gauge adopted by the mainline railways in
Ireland is
1,600 mm (5 ft 3 in). This unusually broad
track gauge is otherwise found only in
Australia (where it was introduced by the Irish railway engineer
F. W. Sheilds), in the states of
Victoria, southern
New South Wales (via some extensions of the Victorian rail network) and
South Australia, as well as in
Brazil.
Ireland's first railway, the
Dublin and Kingstown, was built to 1,435 mm (4 ft 8+1⁄2 in) (later known as
standard gauge). The
Ulster Railway (UR), taking the Irish Railway Commission's advice, used 1,880 mm (6 ft 2 in). The
Dublin and Drogheda Railway was proposed to be built to 1,575 mm (5 ft 2 in) gauge[1] on the grounds of lower costs. The two broader gauges were not used anywhere else. Following complaints from the UR, the
Board of Trade investigated the matter, and in 1843 decreed the use of 1,600 mm (5 ft 3 in).[2]
The UR was
re-gauged in 1846, at a cost of £19,000 (about £1,957,000 today), and the Dublin and Kingstown Railway in 1857 for £38,000 (about £3,857,000 today).
Numerous
narrow-gauge systems were built, usually as
three foot gauge railways (3 ft or 914 mm). Most are now closed, including one of the largest narrow-gauge systems, that of the County Donegal Railways Joint Committee. The Irish narrow gauge today survives as heritage railways in both
the Republic and in
Northern Ireland.
Bord na Móna uses narrow gauge in the Midlands bogs as part of its peat transport network. There is also a private peat railway on the southern shores of
Lough Neagh in Northern Ireland, operated by the Sunshine Peat Company.