There's a movie based on a similar scenario called Unstoppable with Denzel Washington and Chris Pine. It was interesting seeing the creative ways they came up with to try and stop the train.We just had a runaway iron ore train (a very long train with many freight wagons piled high with the mined ore) in that part of Western Australia where the map of Europe doesn't reach - west of the bottom of the map of England there). The train was underway, but then the driver got out for some reason, and the train took off and sped towards a town on the coast, out of control. It covered more than 100kms before the mining conglomerate (BHP) made a remote intervention from their control centre in Perth, thousands of miles to the south. They flipped a lever and the train tracks switched, derailing the train which was travelling at high speed.
Catastrophic as this was financially for our mining operations, at least there were no casualties. If such a thing had happened in Europe, due to the decentralised population everywhere, the outcome would have been far worse.