Ah, yes. I remember, on inter-railing trips, the combined perils of making sure the carriage you were making for was actually going where you wanted to, despite where the 'train' was headed, and making sure you get the best carriage to travel in! A train from Budapest to Prague, for example, could have Hungarian, Czech, Austrian, German and Romanian carriages. On those, you really wanted an Austrian compartment carriage, as you could pull the seats together. End up on a Romanian carriage, and you were sleeping on the floor, with squealing brakes that would wake you up every half hour.

Splitting/combining trains is quite common on routes that have congested mainlines. Commuter trains to/from London do this quite a lot - some Southern Coastway services will even split their 12-car trains into 3 portions en route...