I noticed that in German trains and buses, people are really aversive to sit next to strangers. They would either take the aisle seat to block the whole row to themselves, or they would put a bag/other object to block others from sitting there. Even when the train were totally packed with people sitting on the floor and the conductor announcing to please remove the bags from the seat, they would keep doing that. They don't take the initiative to give space to others when the train or bus is full. Their excuse usually is that "if you really want to sit, you should ask".
But in Spain, I noticed the total opposite trend. Even when the train/bus is totally empty, I often have someone coming to sit right next/close to me.
How do people in your country perceive personal space on public transport?