The Abermule train collision was a head-on collision which occurred at Abermule, Montgomeryshire, Wales, on Wednesday, 26 January 1921, killing 17 people. The crash arose from misunderstandings between staff which effectively over-rode the safe operation of the Electric Train Tablet system protecting the single line. A train departed carrying the wrong tablet for the section it was entering and collided with a train coming the other way.