It was previously illegal to have "illegal" knives on or about one's person, away from one's home/property/workplace, but it now appears that illegal knives are legal to have within one's vehicle. Read your Penal Code, and interpret it for yourself. A switchblade is not a mere illegal knife, so don't consider switchblades for vehicular carry.
As for the lamentations about Bowies, keep in mind that one or two things about Bowies would make them illegal, anyway: size, and more than one sharpened edge. Real Bowies are big, chopping-sized blades, and at least some folks feel a true Bowie must have a sharpened "clip" area. As Rezin and James Bowie made the knife's reputation with big single-edged knives, I don't think a clip point is what makes a knife a Bowie.
Edited to add: I wear a Texas peace officer badge, but do not give legal advice, which is why I so often say to read the Penal Code, and interpret it for yourself. What I would do if I found someone with a knife that is outside the letter of the law is not what another peace officer may do, anyway. (I have only made knife arrests when I had a "turd" in custody, who needed the book thrown at him, period.) Big knives tend to scare the bejesus out of people, including police; I have co-corkers who have just about jumped out of their skins when I have pulled out a 3-inch stout-blade folder. I have been sternly warned by some co-workers that my Strider AR and Al Mar SERE are illegal, when in fact they are perfectly legal for private citizens, and Texas peace officers can carry ANY knife, anyway, regardless of blade length or number of sharpened edges. (Yes, that is in the Penal Code, too.)