As someone who has witnessed a person being run over by a truck I can tell you it is a very ugly event. Still haunts me 20 years later. Trucks cannot see you very well, and even if they could, they can't stop quickly. And when you and a truck collide you lose.
That being said, I resorted to drafting trucks on one long motorcycle trip. I was heading north from New Orleans to Boston in late March. After I entered Virginia the temperatures began to fall precipitously. In an effort to stave off hypothermia I resorted to drafting trucks. Extremely effective. The long term solution, of course, was to limit my riding to the warmer hours and stop more often for hot meals. It took me longer to get home to Boston but I made it in one piece. Had I to do it over again I would have electrically heated clothing.