In the Gemara the two mishnayot that are the subject of our shiur today are parceled together with the previous mishnah. The subject of the Reisha [first section of the mishnah] is obvious: what happens if the time for reciting the Amidah will pass if someone is in a situation in which they are journeying but at the same time they have to maintain control over the means of transport? According to the mishnah, our traveller should dismount in order to recite the Amidah. It would logically follow that it is most untoward that our traveller should recite the Amidah while still riding the donkey. However, the Gemara [Berakhot 30a] quotes a baraita which suggests a different view of the situation. In the baraita two views are expressed: that of Tanna Kamma and that of Rabbi [Yehudah the President of the Sanhedrin]. Tanna Kamma of the baraita only conditionally agrees with the Tanna in our mishnah: our traveller should dismount in order to recite the Amidah only if there is some other person available who will control the animal; if that is not possible then it would be preferable for the traveller to recite the Amidah while still sitting on the donkey and while still in control of the animal. Rabbi dismisses even this differentiation, and has a view completely at variance with that of the Tanna in the mishnah: Rabbi says that even if he dismounts and someone else controls the animal our traveller will not be able to concentrate properly, so it would be best under all circumstances for him or her to recite the Amidah while still sitting on the donkey and while still in control of the animal. The Gemara points out that Rabbi's view is in fact halakhah - and his is also the view enshrined in the great halakhic codes of the Middle Ages [see for example Shulĥan Arukh, Oraĥ Ĥayyim 94:4].
The difference between the situation in Mishnah Six and that in Mishnah Five is that the traveller is not in control of the means of transport, but on the other hand there is no possibility for him or her to dismount or get off. Thus here also the view of Rabbi must prevail.
It seems to me that it would not be prudent to accept this ruling of Rabbi's (and the codes) by transferal to modern means of transport. It is clear that the main concern is an ability to concentrate properly on the task in hand - reciting the Amidah. It seems to me that today, if one is driving a car and the last time for reciting the Amidah is fast waning, that one should follow the view of the Tanna in our mishnah: park the car, get out - if possible - and recite the Amidah with as much concentration as can be mustered. Even if someone else is in control of the vehicle (a bus, for example) it would still be very difficult to muster the required concentration. Indeed, I suspect that most Conservative Jews - even those who try to recite all the daily prayers - under the circumstances presumed in our mishnah would see themselves as having to "pass on this one".
The second topic of both our mishnayot is the question of which direction to face when reciting the Amidah. Our mishnayot speak of "directing one's face", but this is not explained. The Gemara explains the concept from a baraita, which is so clear and straightforward that I shall just quote it "as is":-