If a person traveling by bus or car slept and woke up to find himself in a state of Janabah (major impurity due to intimate relations, a wet dream, losing consciousness, ...), and it was time for the Fajr (dawn) prayer when the bus stopped before a masjid, what should he do? There was water for Wudhoo’ (ablution) but the number of passengers with him on the bus was not small. Kindly answer, may Allaah reward you.

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

That person has to do his best to perform Ghusl (shower to purify from major impurity) to remove the state of Janabah, as long as there is enough water. When one is in a state of Janabah and there is water available and he is able to use it, prayer is invalid unless he makes Ghusl. Allaah Almighty says (what means): {And if you are in a state of Janabah, then purify yourselves.} [Quran  5: 6] 

Also, the Prophet said: "The prayer of one of you is not accepted when he is in a state of impurity unless he makes Wudhoo’." [Al-Bukhari and Muslim; this is the wording of Muslim]

But if there is not enough water for Ghusl or there is not enough time, then Tayammum (dry ablution) is the alternative in this case. He has to make Tayammum and there is no harm in this Inshaa' Allaah.

Allaah Knows best.