Here's a problem you don't encounter in the finescale model railway world. I was helping a friend set up some Lionel trains track - three rail chunky stuff that would give an MRJ subscriber and attack of the vapours - and once we'd clipped it all together, he handed me a bag of joiners.
These slide under the sleepers at the end of each length of track and stop them working apart. With Lionel trains being made of cast iron and weighing about half a ton each, it seems that as they round the bend, something they are perfectly capable of doing at speed, they can cause the track to "walk" and the joints to open up. Do this too much and the lines splits producing a crash not unlike the final scenes of the 1976 film "Silver Streak".
The joiners are a bit of a fiddle to slide under the sleeper. I found that if you squeezed the nearest ends together you could slide the plate in place and then with a good shove and some sore fingers, use it to pull the rest of the sleeper over.
Presumably this all worked because there was nothing on the local news along the lines of "Small child killed by derailing toy train", although since the stand was promoting the L&WMRS exhibition, it might have garnered plenty of press coverage if it had !