...The semi was headed west when its raised bed slammed into the overhead sign near mile marker 200 as it approached the I-64/I-295 split.
Virginia State Police said the crash happened shortly after 9:30 a.m.
"The cab continued on and then stopped, obviously, because it had separated from the bed of the tractor-trailer," Matt Demlein, a spokesperson for Virginia State Police, said. "We're still investigating as to what led up to it actually hitting the sign. It was empty at the time."
Troopers do not know why the bed was raised or how long it was up before the crash. But officials said the truck had stopped at a weigh station about a mile earlier, which is equipped with cameras...
Probably one complication is that the trucks need to be able to drive while the bed is up in normal operation. They have to move forward while dumping to spread the load.
But realistically, there's no reason why you can't design the hydraulics in a way that the cylinder is always leaking through an orifice and the dump trailer is constantly slowly lowering itself unless you are actively holding the Up button. There's never a case where a truck needs to hold it's dump up in the air for long periods of time.
He might not have been fully up to speed yet. This sign is just past a weigh station (I've driven this stretch many, many times), and VDOT said he had just gone through the station. Though that doesn't answer why the bed was up. Could have bumped the switch?
:::Edit to strike through this nonsense:::I am leaning toward the other explanation of drive shaft breaking and pole vaulting the trailer into the sign.