How can a women travel without a mahram

Each year i used to go stay with my grandparents who are at a different region where it takes half a day to go into in bus and i would stay there for more than one month. I do this to give them company and assist them as they are really old. But recently i learned that it is haram for a woman to travel alone but my only mahram is my father who cant travel due to being weak because of healt issues. And if i am almost obliged to go because if i dont my grandparents will be really sad and angry with me and it will cause some drama in the family. Then can i still go alone as i have done it for a long time and never had any problem whatsoever?