On August 25th, 1861, a passenger train slams into another in a mile long tunnel on the Brighton Main Line in Pyecombe, West Sussex England.
It happened when two signalmen, one on each tunnel end, made a telegraph message error about whether or not the tunnel was clear.
It was the worst accident British railway system witnessed for the 19th century.
Yet, it became an aspect for some development for Signaling Block Systems which ensured some certain minimum distance between traveling trains.
Still, let's hope not to see this happen all over again.
Credit to Oliver11GWR and various artists for the instrumental tracks featured.