A:
The intention to shorten Salah should be made before performing the Salah itself not on traveling, as the Prophet (peace be upon him) said,
Actions are judged by intentions.
Therefore, if you travel without making intention to shorten Salah, it is permissible to make your intention before you shorten the first four-Rak`ah Salah (Prayer consisting of four units), if the distance of the journey is over that which it is permissible to shorten Salah, which is about 80 kilometers.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.