The Torah says mipnei seiva takum, that one must stand for one elders.
I was wondering, it is common practice on public transportation such as buses (very common in eretz yisroel) to offer ones seat to an older (over the age of 70) person. Is there an halachic obligation to give ones seat to the elder, or although not thoughtful, is it enough to stand for them but not to give them the seat. Are there any sources that discuss this.