Tauernbahn
The Tauernbahn is a railway through the mountains in Austria, called the Hohe Tauern. Many freight trains travel over the Tauernbahn. These trains run between western and southern Europe. Around 1975, the Tauernbahn consisted of single track on large parts of the route. And because many trains came from all directions of Western Europe, they had to wait before they could enter the Tauernbahn. This is what these trains did and still do at Schwarzach-St.Veit station.
The Tauernbahn is too steep for many freight trains. This is why extra locomotives are added at Schwarzach-St.Veit station. Often, one extra is put in the middle and one behind the freight train. This keeps the coupling between the freight wagons intact and prevents the train from breaking in half.
Below you can see the route of the Tauernbahn to scale, as built in 1905 and the changes until 2010.