Davening on a bus

Q: Is it permissible to daven on a bus while seated?
A: It is clear that a bus is not a great place to daven, and it is difficult to concentrate on a bus. Sitting is also not appropriate, since one needs to pray as if standing before a king. But we must differentiate between when there is a choice and when there is no choice. If a person is on a bus for some reason and he will miss davening since he will arrive too late then it is preferable to daven on the bus. If it is possible to stand – he stood stand; if it is impossible – he should sit. But if there is a choice then he should certainly daven in the proper frame of mind in an appropriate place (Shut Be'er Moshe 3:14).