During your Eurail trip, you can hop on and hop off most local and regional trains. If you plan to take a high-speed or night train, you may need to buy a compulsory reservation in addition to your Eurail pass. This will depend on the countries you travel in and the type of train you take. This reservation guarantees you a seat or sleeping accommodation on the train.
For most high-speed and night trains it is mandatory to make an advance reservation. These reservations can help make sure you get a comfortable and stress-free journey. Here are some of the benefits to making reservations:
Be sure of a seat on a busy train, especially during the peak season (May-September and during European school vacations) when trains can get pretty packed.
Sit together – if you’re traveling in a group.