I couldn't help but think of this thread today.
A friend of mine was hauling his mini-ex, on the interstate, when an 18 wheeler driver with his head up his ass, decided to change lanes, while he was right beside my friend. Hard braking, and a sudden swerve avoided a collision, but the end result was my fiend's truck facing north, in the southbound lanes. (Actually, on the southbound shoulder.) Damage was limited to the trailer's fender and three sections of guardrail. The machine ended up closer to one side of the trailer than the other, and needed to be re-positioned and re-secured, but the chains kept it on the trailer.
The chains not only kept the excavator from being part of the wreck, they very well might've kept somebody's family from becoming part of the wreck too. Lots of laws are laws because they're written in blood...