Is the presence of a mahram required when driving a brother’s wife a short distance?

Question:
May Allah reward you, Honorable Shaykh. This questioner says: If I drive my brother’s wife to her parents’ house, even though they live in the same neighborhood as us, is it necessary for a mahram to be with us?

Answer:
If you are walking on foot, that is one thing. But if you are in a car, there must be someone present whose presence removes the seclusion (khalwah). If two or three women are present, there is no harm; the seclusion is removed. But if there is only one woman in a car, no. Yes.