My girl is now 2.5 years old and every time I let her stand on the platform waiting the MTR door to open, I will say "請先讓車上乘客落車,多謝合作", 每次有人讓位, I will ask her to say thank you to that good person, and till her next time when we saw auntie with big tummy or elderly, we will let them sit.
there was a time when i was in the mtr, i saw a pregnant woman standing and no one wanted to give her the seat. so i said on the phone quite loudly to my friend and that those guys are terrible and selfish. yet, they heard me but pretend nothing happened. if i were the pregnant woman, i would have told the men off and said i needed to seat.