My wife used to ride in the car with her legs open in a skirt (didn't wear panties for years), totally topless, etc when we had to drive a regular 15-hour drive over the course of a few months.
We were in a pretty high SUV, and we never noticed truckers looking except just one time. A guy in a small cab (not sleeper) without a trailer stared at her through his back window for a mile or so; my wife was topless and her legs open without panties. At first she freaked out and covered her boobs and closed her legs, but then she gave up and let him look. He slowed down until the cars behind him started flashing their lights (he was in the left lane pacing us now), and he finally took off down the road. Really young guy; probably new at driving a truck locally and she was his first sighting.
Other than that, we never saw a trucker even look in our direction, to be honest.