Train reservations are optional, so where to sit?

German long-distance ICE trains typically have some sort of indicator above the seat, showing if the seat is reserved. It is not obvious.
Other trains may have little slips of paper with the same information.
Otherwise, you just ask. Do not be afraid to do so, it is perfectly acceptable behaviour!

Generally speaking, on German distance trains, there are small electronic signs on the sides of the seats or just above them that list the cities between which sears are reserved, so for example Freiburg-Karlsruhe would mean someone has reserved the seat for that portion. Sometimes these signs are not working, usually with the message ggf. reserviert, In this case it is not possible to know if the seat is reserved or not, so you just sit where you want.

In either case, if you have reserved the seat, you can certainly ask the people sitting in it to move.

On Swiss trains that have reserved seats, the reservation in usually indicated by a card clipped in a holder above the window or the seat. It may be reserved for a later section of the route—-as I recall, it says the point from which the reservation starts. But it is best to take a seat without any reservation so you don’t have to move later.

If you board the car with your reserved seat and it is occupied, then you do just politely point out the reservation and ask them to yield the seat.

Hello, Carrie.

On Swiss and Austrian trains (I mention Austrian trains because many operate in Switzerland), you will find paper reservation tags on a matrix at the door to each compartment or above each group of seats in an open coach. The newest Swiss trains have tiny electronic signs.

Historically, reservation tags showed last name, origin and destination. Now, they just show origin and destination.

On German trains (your train to Freiburg would either have used Swiss or German cars), there are tiny electronic signs indicating reserved seats. Very often the signs don't work or the reservation set hasn't been loaded by the train crew. You might see "Ggf. reserviert" (might be reserved) or "Ggf. freigeben" (might not be reserved) for most or all seats.

Also note that paper reservation tags can only be placed if the reservations are made a few hours before the train leaves its point of origin. Electronic signs can technically be updated mid-route, but in practice, this isn't done. Accordingly, if you reserve close to departure, you'll be placed in one of a small number of generically designated last-minute reservation seats. On Swiss trains, these are more or less permanently marked, and people in the know won't sit there unless the train car is full. On German trains, you may see "Ggf. reserviert", but Germans are as confused as you about what it entails, so they will sit down regardless.

It's fine to ask people to move if they are indeed in your seats. Double-check the class, car number and seat number. Also note that on German trains, reservations expire if not claimed 15 minutes after departure.

As for French trains, which also operate in Switzerland, France has done away with reservation markings, as all French high-speed trains (including the TGV Lyria to Switzerland) require reservations for cross-border trips, so every seat is reserved and everyone has a ticket with a specific car number and seat number. This can cause confusion when you are taking a domestic trip on a French train operating outside France (more common in Germany, for example, Stuttgart/Karlsruhe on a TGV to/from Paris). In that case no reservation is required and you just look for an open seat, being prepared to move if someone who has a reservation for a cross-border trip comes to claim your seat.

Reservations are nice to have at busy times. Sometimes they pay off and sometimes they don't, but for a few euro or a few Swiss francs, I think it's worth the gamble.

Thanks for the quick responses and very helpful information. I want to make sure I do things correctly for future trips.

I don’t recall seeing any reservation indicators, but of course I wasn’t looking for them as I was not aware of their existence. I’ll keep an eye out on future train travels.

I figured it was ok to ask the people to move, but we were trying so hard to just blend in and not cause anyone any trouble on our account. And, as there were other seats available, it wasn’t an issues. But, hopefully, we didn’t take someone else’s seats. 😊

If there were plenty of seats, no harm no foul.

My DH and I once had to move from seats on an ICE train because a man AND HIS DOG had reserved those seats minutes before at the station. 😁

I figured it was ok to ask the people to move, but we were trying so
hard to just blend in and not cause anyone any trouble on our account.

You should genuinely not feel strange about doing this (after you double-check to make sure you are in the right train car and at the right seats, of course!). No one will think it is odd and you are not causing trouble; you have paid for the reservation and have the right to use it.

I've been on plenty of German trains that had indicators over the seats to say for what segment they were reserved. On December 26 of 2001, I was on an ICE from FRA to Karlsruhe. It was holiday, the second day of Christmas, and the train was packed. We had to stand in the aisle at first. We could tell by the indicators over the seats that few were actually reserved, just already occupied. When we got to Mannheim, people got up to get off, and, before more came on, we took two of the unreserved seats.

In November of 2008, I had tickets for three legs (IC/ICE/IC) of long distance trains with a Dauer-Spezial (now SparPreis) ticket, along with seat reservations, which were at the time included with advance purchase tickets. Due to wheel problems on these trains, different types of carriages were being substituted. On some, my assigned seat didn't even exist.

The first train, an IC, had a different type of carriage, but it was only partially full, so I had no problem finding a seat. The second train, an ICE, was sparsely filled. I missed the last train, an IC, due to my connecting train being late, so they put me on an ICE, without a reservation, but that train was only partially filled, as well.

The only problem I can foresee would be if you had reserved facing seats with a table between so, for instance, you could work with your computer, and your seats were filled by squatters and there were no other like seat combinations available.

I remember hearing a story years ago from a guy who boarded a train in Florence and found his reserved seats occupied. The occupants insisted that they had the seats reserved.

When the conductor was called, he looked at their tickets and reservations and remarked that they were only valid to Firenze!

"But we bought tickets to Florence", they argued.

"Yes," the conductor told them, "but Firenze is Florence, and we just left it."

At that point the squatters insisted that the engineer back the train up to Firenze so they could get off.

Consider this though -- I once reserved a seat at the table spot in the carriage because that's the one I wanted, and when I boarded a single mom with a toddler, a baby, a folding stroller, and bag after bag of supplies was in my spot. She saw me looking and said that her seats were on the top level of the car but because of the kids could we trade/switch? Propriety dictated that I not refuse, and the upper level seat was more cramped and more noisy, and not what I'd paid for, but better that I suffer /s than she, no?

There are signs as others have said. So they might not have known or not have cared. You can politely point out they are your seats and ask them to move. Otherwise get the conductor/ticket agent involved. I usually reserve seats with a table as there are usually 3 of us and we like the use of it. Don't feel guilty about making people move.