I see people in flat bed trucks bouncing up the freeway regularly with open boxes of nails in the back bouncing around.
decades ag, when they changed over the SF Bay Bridge from busses & trucks on the lower deck, and cars on upper, to both, on each deck. That meant they had to add clearance to the upper level Yerba Buena Island tunnel, and create a transition during construction: "The Hump".
During one morning's rush hour, one of those jockeys hit The Hump, and dumped two KEGS--not boxes--of roofing nails, which spilled across all lanes heading into the city. Hilarity ensued for hours.