Travelling is defined by case law. Generally, case law has held sucessful defense of Unawful Carry of Weapons (UCW) charges in cases where:
1) The trip involved crossing at least two county lines; and
2) An overnight stay.
The change in law went from making "travelling" a "defense to prosecution" to making it an "exception." (moved it from PC 46.02 to PC 46.15). A defense to prosecution needs to be proven in the affirmative by the defense attorney in a pretrial hearing before the judge. If proven, the case goes away. An "exception" actually means that if the "travelling" exemption exists, there should not be an arrest. Note that all of the Peace Officer stuff is an "exception"; there was actually legal authority for a peace officer to arrest another peace officer for legally carrying their sidearm until this changed a few years ago.
What does this mean in the real world of Texas law enforcement? Probably not much. I have never seen or used this law in my several years of working. The only one that came close was a guy from a couple of counties away who was in town for a car show and waved a gun at other motorists who cut him off (and there wasn't enough to charge him with Agg Assault). He could have possibly used travelling, but plead out instead.
Bottom line is that travelling will depend entirely on the often incorrect interpretation of the law by an officer on the side of the road, and will be further clarified by what the local County Attorney thinks he can and should prosecute. If you were just carrying, it will be a diferent than if you were waving it at other motorists. If it worries you, get a CHL or carry a long gun (that's why God gave us gun racks).
BTW, I am not a lawyer.