Relinquishing a Seat to an Elderly Person on a Long Journey

Hello, I live in Tiberias and study in Jerusalem. Sometimes, the bus is full and then an elderly person gets on and wants my seat. The problem is that I am unable to endure a two-hour journey standing, so in such a case, I get off the bus and wait about half an hour for the next one. Am I obligated to do this, or in this case, is there no obligation of 'Mipnei Seivah Takum' (rise before the elderly)?

Greetings,
It is important to clarify things. The commandment of 'Mipnei Seivah Takum' does not mean to get up and vacate your seat. It means to rise in respect of the elderly and then sit back down in your place.
There is a mitzvah of kindness. When someone who finds it difficult to stand gets on the bus, it doesn't matter if it's a disabled person, an elderly person, a small child, a pregnant woman, a young person with joint pain in the knees, and there is a person who is capable of standing, and sitting is not essential for him, it is appropriate for him to give up the seat and give it to the one in need.
However, if the sacrifice is too great, because it is very difficult for you to stand on a long journey, there is no obligation to give up your place, and although it is clear that the elderly person cannot stand for a two-hour journey, he can wait for the next bus, and you are not obligated to get off the bus for this reason.

Shulchan Aruch (Yoreh De'ah, Chapter 244).