بسم الله الرحمن الرحيم

If the water of the carriage (in which one is travelling), as well as the adjacent carriages which he has access to, has finished and before the time of ṣalāh expires, the train is not going to stop at any station/junction for the amount of time in which he can do wudhu or get water to do wudhu, then it will be permissible for him to do tayammum (in Sharīʿah) This is even if he can see water while the train is moving.

أفضل التطبيق العصري على مسائل القدوري

للمفتي محمد أشرف الاشاعتي

Vol.1 Pg.166