In a letter to her mother, Blessed Elizabeth of the Trinity advises:
P.S. Remember to pray while you are on the train on Friday, as that is a very good opportunity for prayer.
Likewise, Jacques Maritain:
One can pray on the train, in the subway, in the dentist’s waiting room.
This is very astute. It’s also dear to my heart. I love to pray on buses, on the subway, on planes, and on trains.
Humanly speaking, there is good motivation. While sitting on these modern forms of transportation, there is a silence; but it is not absolute. We are still with our brothers and sisters; we can notice them and their struggles, without be obtrusive, and gather them into our prayer also, taking their troubles, apparent and unseen, to Jesus’ feet.
Also, there is something in the economy of salvation, as administered by the Church. Travel by trains, buses, and airplanes is (partly) under the patronage of the angels. Raphael the Archangel is, as per his role in the Book of Tobit, patron saint of all travellers. Other angels are patrons of those who travel, especially by modern means. So perhaps, being with the angels and the Church of Heaven, we are well advised to take the opportunity for prayer, too.
And, of course, any time to be alone with the angels and, in particular, our guardian angel, is good for us.