Is it permissible to pray on a train and to combine and shorten prayers for a traveler?

A traveler by train, like any other traveler, is recommended to shorten the four-rak'ah prayers to two rak'ahs if his travel distance reaches the distance of qasr. It is permissible for him to combine Dhuhr and Asr prayers, and Maghrib and Isha prayers, at the time of either of them. The best option for combining is what is more convenient and easier for him. It is permissible for him to pray standing in the train if possible; if he is unable, he may pray sitting. Standing is not waived unless there is an inability to do so.