Is it permissible for a wife to travel alone without a mahram a distance of two or three hours by train or bus within the same country for the purpose of work?

It is not permissible for a woman to travel without a mahram, whether she is married or unmarried, whether her travel is within the country or abroad, or for work or other purposes. This is based on the Prophet's (peace be upon him) saying: "No man should be alone with a woman unless she has a mahram with her, and a woman should not travel except with a mahram." Every journey that is considered travel is forbidden for a woman without a husband or a mahram.