That happens more often than you'd realize. One fella locally was very proud of his new chevy pickup he'd recently modified and was at the gravel lot having them load his truck down with all it would hold. He kept an eye on the springs as they loaded, stopped them once it was setting on the overload springs.
He made it about a mile down the road before having to do a quick stop going down a rather steep hill. The gravel came through the front of the bed and into the back of the cab. There was almost as much gravel in the cab as was remaining in the bed...
Well, the other thing that happens with not-so-new trucks is that the gravel doesn't so much push through the bed and cab, but push the truck, bed, cab and all past what the brakes are capable of holding, right on through the intersection, stopped car, whatever...
Did an errand for a landlord I had fresh out of college. I had a beater shortbed S10, and he had a dogpen he wanted to keep his dog from digging out of...I didn't realize his intention at the time, but he directed me turn-by-turn to a gravel pit, threw a tarp in the back, and had the guy running the loader fill it to the bedrails with crusher fines. If it weren't for owing him a serious favor I'd have been chewing him up one side and down the other, but as it was I just grit my teeth and bore it, because I kind of liked sleeping under a roof. We were way past overloads, the tires were squatting down almost to the rims. He could tell he was pushing my buttons, but was one of those guys who knew exactly where the lines were by reading people and somehow get everything he wanted and not get punched in the face. Weirdest part is I still like the guy.
Backroads home, driving well under the limit with the flashers on and we're going up a hill with a railroad crossing partway up. I'm in first and my foot is flat on the floor, and we're coming up to the crossing. I seriously did not want to have to do a cold start on this hill. He starts looking over at me as we get closer and closer to the crossing. Finally gets to be too much and he actually asks if I am going to slow down? I look over at him and grin, keeping my foot right where it is, payback for messing up my truck without asking. The slope rolls over to level for the crossing and I back off it at the last second to let the hill slow me down, roll over the flat and get right back on it, easy as you please without losing a lick of speed (may have been all of 5mph). We got the last mile to his place without further incident. Good thing for him it was enough gravel for what he wanted, because he wasn't going to get me to go back for more, favor or no.