The messenger of Allah (SAW) said: Three supplications will not be rejected (by Allah (SWT)), the supplication of the parent for his child, the supplication of the one who is fasting, and the supplication of the traveller.

 

During travel supplication is heard by Allah (SWT) if the trip is for a good reason, but if the trip is for a bad intention or to perform illegal things (doing sins) this will not apply to it.