Ruling on shaking hands with the husband's relatives and riding with them

Question:
Is it permissible for a woman to shake hands with her husband's brother, and to ride with him alone in a car?

Answer:
A woman is not permitted to shake hands with her husband's brother, nor his paternal uncle, nor his maternal uncle; because he is not a mahram (a relative one may not marry). She is not permitted to shake hands, nor to be alone with him in a car, nor anywhere else; because he is not a mahram. Her mahrams are her father, her grandfather, her grandfather's father, and the like, and her sons. As for his brothers, paternal uncles, and maternal uncles, they are not mahrams. She is not permitted to shake hands with anyone who is not a mahram for her, and she is not permitted to be alone with anyone, not with the driver, nor with anyone else.