Is it permissible to combine and shorten the Dhuhr and Asr prayers to two rak'ahs when traveling, after the Dhuhr or Asr adhan?

It is permissible for the traveler to combine and shorten prayers. He may combine Dhuhr and Asr, and Maghrib and Isha, and shorten the four-rak'ah prayers. It is a jam' taqdeem (combining by bringing forward) if the time for the first prayer enters while he is still at his residence, and a jam' ta'kheer (combining by delaying) if the time for the first prayer enters while he is on the move, in which case he delays the prayer until he settles. The ruling of travel begins after the traveler has passed the houses of his city.