Today marks the anniversary of a serious accident on the Great Western Railway at Norton Fitzwarren in 1940. 27 people were killed, and a further 75 were injured when their express sleeper train from London (carrying over 900 people) passed two signals at danger, derailed and overturned. The accident occurred at about 3.45 a.m. on a very dark, wet and windy night.
The train had been routed from the main line to a relief line at Taunton, to allow another train (carrying newspapers) to pass. However, the driver was under the impression that he was still on the main line and continued to accelerate until he realised his error. By that time it was too late to bring the train to a halt. The train went through a set of catch points at about 45 mph (there to protect the main line). The locomotive tipped onto its side and the first six coaches telescoped into each other, blocking all four tracks. Luckily, the newspaper train had just passed the express - had the two trains collided the casualties would have been far greater.
The causes of the accident still feature in rail accidents today. The driver, with over 40 years' experience, was probably operating on 'auto-pilot' - his experience worked against him as his actions became subconscious; including cancelling two warnings from the automatic signalling system. He had also lost his 'situational awareness', being unaware of which line he was running on; he had never before been diverted onto this line and the signals that applied to him were on the opposite side of the track from normal practice. Fatigue and other psychological factors were also likely to be present; the train was working during wartime blackout conditions, during the night and his home in London had recently been damaged by bombing.
You can read the accident report on the Railways Archive website, and the story is told in detail in this contemporary newspaper report.