This idea has been done, but it does not work by trying to grab on to the suction behind a large truck because that suction would have to be a perfect vacuum in order for it to pull you, but large trucks do also create a strong cross wind as they push thru the air and someone has built and tested a vehicle that took cross wind and made it in to forward motion with a wing of sorts, because just like with a sail boat you can not travel in the same direction of the wind as fast as that wind.
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So yes, the idea of a sail can be laughed at but that is mostly because a sail works as a wing, not a cup that catches the wind, a wing creates lift and when put on a boat or a car that lift is turned in to forward force so a 15mph wind can push you forward at 30 or 40mph.