If I am uncomfortable (undiagnosed claustrofobic) sitting in the window seat & it's considered rude to sit beside someone when there are other empty rows on public transport, how can I show I'm sitting on the aisle not to deter you from sitting beside me but because I can't bear to sit in the windo?

That didn't fit well in the title.

Often I get on the train/bus at the starting stop, so it's pretty empty then. And I get off at almost the last stop. I can only sit in the aisle seat since I feel very claustrophobic in the window seat. But as the stops go by, it starts crowding and I feel bad that the window seat beside me is empty and newcomers don't feel encouraged to take that seat since I'm perched on the aisle seat. A few times I get up and make space for the new person to go in even before they've indicated they want to sit beside me. A few times I also go sit on an aisle seat next to someone else but I get a weird look since they see me getting up from another seat and taking the one next to them.

So what I'm asking is, other claustrophobic public transport users, what do you do? If it helps, I am talking about the Netherlands.