Railway signalling is a system used to direct
railway traffic and keep trains clear of each other at all times. Trains move on fixed
rails, making them uniquely susceptible to
collision. This susceptibility is exacerbated by the enormous weight and inertia of a train, which make it difficult to quickly stop when encountering an obstacle. In the
UK, the
Regulation of Railways Act 1889 introduced a series of requirements on matters such as the implementation of interlocked block signalling and other safety measures as a direct result of the
Armagh rail disaster in that year.