This is one of my favourites, snatched from a train window during a monsoon in April 2012. We had gone for a weekend to Somerset with some friends, an annual ritual. It literally poured with rain from the moment we left home until we got back. Being determined not to let rain stop play we carried on with umbrellas and coats.
This is the heritage steam West Somerset Railway. Rain very nearly did stop play at one point because floodwater can move ballast and track and it is impossible to see what is happening in the muddy water.
We were stuck at this station, on a siding with no platform for about 40 minutes because the train coming the other way had problems in the flood. Here is the point when we were able to proceed. Before radio, electronics and all our modern safety systems this was it. It was very simple and utterly fool proof and fail proof. Each section of track has one token. You cannot enter the section without the token. That is all there is to it. Here the driver is receiving the token for the next section that has just arrived on the train coming the other way. Normally the trains would pass close to each other at the station and the large loop on the token is to make it easy for one driver to pass to the other driver while the two trains are moving. The receiving driver would stick out his arm and the other driver would use the loop to place it over the arm. This reduces the risk of either driver dropping the token.
The token system was developed in Britain in the 19th century, to enable safe working of single-line railways. If a branch line is a dead end with a simple shuttle train service, then a single token is sufficient. The driver of any train entering the branch line (or occupying any part of it) must be in possession of the token, and no collision with another train is possible.