The Armagh rail disaster happened on June 12, 1889 near Armagh, Northern Ireland. At the time it was the world's worst rail disaster. 88 people were killed, most of them children, and 170 injured.
Armagh Sunday school had organized a day trip to the seaside resort of Warrenpoint. A special train was arranged for this occasion, carrying almost 600 passengers. To sell more tickets, three extra carriages had been added at the last minute - the extra weight from these meant that the locomotive had barely enough to power to pull the train out of the station.
The train set off at 10:20 AM. As the train left Armagh, it was faced with a long uphill gradient of 1 in 75. The underpowered train almost reached the top, before the engine stalled 200 yards from the summit. The train's braking system was continuous non-automatic vacuum, meaning that all the carriages had brakes, but it was not automatic. In the 'non-automatic' brake system a vacuum had to be created in the system to apply the brake and allowing air to enter the system released the brake, whereas in the 'automatic' system the creation of a vacuum in the system releases the brake and allowing air to enter the system, for example when brake pipes are disconnected, applies the brake.
To get the train over the summit, the driver decided to split the train in two. As the rear section of the train would be left without brakes, the train crew placed stones behind the wheels of this section, as well as applying a hand brake in the guard's van. Unfortunately, the engine had stalled with its pistons in the "dead centre" position, meaning that when it was restarted to take the front section of the train over the summit, it move back slightly, crushing the stones. The hand brake alone was not sufficient to hold the rear section, which rolled away down the hill. The occupants were unable to escape as the doors were locked to stop entry by fare-dodgers.
Meanwhile, the 10:35 had left Armagh. Its crew were horrified to see ten carriages careering backwards towards them with people jumping off the running boards and children being thrown from the windows of the locked carriages. The 10:35 braked, and slowed to 5 mph, before being hit by the runaway carriages, travelling at 40 mph. The final three carriages and occupants were totally destroyed.
As a result of the disaster, the UK Parliament passed a law, the Regulation of Railways Act 1889, which made continuous automatic brakes mandatory on British passenger railways, along with the block system of signaling and the interlocking of all points and signals.