Who is responsible for picking up and dropping off child?

I live in a different state then my child, I always pick my son up when he coming to visit me and his father always pick him up when he go home. This time he refuse to pick him up and its hard for me to travel on a bus because I have problems with my legs. I usually get a ride half way and he meets me, we never discuss how he was getting back because he always pick him up. Am I responsible in getting my child back home.