I got this from one of my brothers today. He had to hit the brakes for a snow plow and his load kept going. He would be dead if it wasn’t for his massively overbuilt chain rack on the back of his truck. That is 46,000 lbs of steel that slammed into his cab. He SHOULD have had a chain on the front to prevent this. I think he will in the future. He is lucky to be alive. If you are hauling anything, make damm sure it can’t move.
Have seen truckers build slide barriers out of 6x6's and chains for this type of cargo (long slidy stuff). Many a log hauler met their maker due to logs coming through the cabs. I cringe if I see one pulling a load without a headache rack.
This happened almost 20 years on I-565 in front of the Hsv. Space and Rocket Center. Spare tire got loose, went into oncoming traffic. Fortunately the driver, my wife's boss at the time, was unhurt.