The real classic on the subject of railway safety is this this:
https://www.amazon.com/Red-Danger-Classic-History-Railways-dp-0752451065/dp/0752451065/We all read it when we were young. Written by the well known Tom Rolt, manager of the first preserved railway: Tallyllyn.
It describes the stage-by-stage development of railway safety in the UK, through the investigations and recommendations by Her/His Majesty's Railway Inspectors of railway accidents.
Describes the British system, which differs a lot from both the rest of Europe and naturally from the US. The British system was developed as a response to the high traffic density, short trains, high speeds and rather feeble brakes.
Added:
As you say, nice video but rather basic.
Towards the end of the video where he describes the Tyer machine, he also mentions the Abermule train crash:
https://en.wikipedia.org/wiki/Abermule_train_collisionwhich has a great significance in British safety development and also in the book.
It was also referred to in a very recent investigation of incident on the Romney Hythe & Dymchurch 15" miniature railway, where two trains were on heads on collision course. They were able to stop in time thanks to good visibility. But it is interesting that the crash exactly a century ago is used as reference.