I have drafted logging trucks and dump trucks before. Logging truck was okay to around 40, then my legs got tired. The dump truck was another story. A fine draft well into the 40's. The problem began when I chose to leave the draft and fall back to the group that missed "getting on". Coming out of a draft from such a big tall truck was unnerving. The turbulence 30 to 50 feet behind the truck was scary. My drafting days are over.