The observant of us will notice that this is a passenger train.
It’s a traditional loco hauled design, something that is becoming a minority in many places as multiple units (engines under the floor) become increasingly common. So nearest us is the locomotive which contains a really big engine and associated bits and hauls the rest of the train.
Right? No, wrong. That’s not a locomotive. It’s a DVT. No, not DVT. A DVT. It’s a kind of dummy loco with a driving cab at one end and depending on the maker and operator may have (and does in this case) auxiliary engines for brakes and electricity. Sometimes it’s an empty space which may be used for luggage, bikes and the guard’s office. The actual loco is one of these, a GM model with an ancient and filthy EMD two stroke. Diesel locos are about the only American rolling stock to be found in Europe as they’re something of a niche market here.
So why do we want a DVT? Because the other choices are to have a very expensive loco at each end which is usually unnecessary for a passenger train or do a spot of time consuming shunting with one loco (uncouple it, transfer to a parallel line, recouple to the other end) or two (drive in with one, leave it there and then get hauled out by another which attaches to the end).
So there we have it. How to drive a train bi directionally with one locomotive.