Is it permissible for a man to help me get on and off transportation?

It is permissible for a woman to ride in a taxi alone with a non-mahram driver out of necessity, and when there is no mahram or woman to accompany her. Necessity is assessed by its extent. However, without necessity, it is not permissible. The ruling is relaxed for an elderly woman who is not desired, and it is stricter for a young woman. The stronger the potential for fitna (temptation/strife), the more stringent the matter becomes and the greater the need for precaution.