I am looking to take the Golden Pass line with my EU Rail pass, is it necessary to make reservations on it? I am planning on going from Lucerne all the way to Montreux, but will make a stop in Interlaken. I'm not exactly sure when I want to take each train on the line, which is why I would rather not make reservations if it is not necessary. Thanks!
You don't need reservations. You only need reservations if you want to ride in the few special seats up by the train drivers.
You're not "required" to make a reservation and you only "need" a reservation if you absolutely want a seat. The GP I was on in June several years ago was sold out, and the young lady occupying my reserved seat was quite distraught when I arrived and she had to vacate.
Thanks for the responses! If the train is sold out, do I just have to stand on the train, or am I not allowed to even be on the train?
The thing to realise is that the Golden Pass line is neither one line nor one train, just a tourist naming of a series of lines.
It is the rail route Luzern - Brünig Pass - Interlaken - Spiez - Zweisimmen - Montreux
This route, like all other rail lines in Switzerland, has at least one train per hour. You can travel on any of the trains, and get off and get back on one hour later, no reservations needed or usually possibly.
There is no through train, you always have to change trains at Interlaken and Zweisimmen, and usually also at Spiez.
The Golden Pass train is an extra train for tourists with panoramic windows, and you can reserve seats on this train. You still have to change trains at Interlaken and Zweisimmen.
Since you don't have to reserve, it can't be "sold out".