889. The second condition: The place for prayers should not have such a vigorous movement which would make normal standing, Ruku’ or Sajdah impossible. In fact, as an obligatory precaution, it should not prevent the body from being at ease.
But if one is forced to pray at such places, due to shortage of time, or any other reason, like in a car, on a ship or on train, then one should try to remain still, and to maintain the direction of Qibla, as much as possible. And if the vehicles move away from the direction, he should return to Qibla.