[wongarsu]

If it's gravel they are transporting it's obviously their fault, it's the responsibility of the driver to secure the load (with some blame falling on truck companies for providing insufficient equipment).

If it's random gravel from the road it's more understandable. But even then the driver is very much responsible for the mud guards on the truck they are operating, just as the police would write a ticket to the driver for worn down tires or broken lights.

[andrei_says_]

But are they “a punch in the face”-responsible?

I lived in Boston for a while. Cracked windshields were extremely common. No one was ever upset at another person.

[squeaky-clean]

I think you're missing the joke. If truck drivers could actually put up a sign saying they are not liable for any debris falling from their vehicle, and have it be a valid defense in court. Then they would just put up a sign saying they are not liable for any black eyes given when they see debris falling off a truck.

They're taking the unrealistic expectation of the truck driver's sign protecting them from doing something illegal and flipping it. In other words "If you coul just put up your own sign and get legal protection to break my windshield, then I could just as easily put up a sign giving me legal protection to break your nose."