Cargo: weight, securement and inspection
You're responsible for your cargo, even if someone else loaded it. That means making sure it's secured and within weight limits, and checking it as you go.
GVWR is the maximum loaded weight a single vehicle is rated for. Overloading makes braking and steering worse and is illegal. Even with a sealed load you can't inspect, you're still responsible for staying within gross and axle weight limits.
Keep heavy cargo low. Stacking weight high raises the center of gravity and makes rollovers more likely. Use blocking to keep cargo from sliding, and tiedowns to hold it down: at least one tiedown for every 10 feet of cargo, and never fewer than two. A strong header board protects you from cargo sliding forward in a sudden stop. Cover cargo so it can't blow or spill onto the road.
Check your cargo and securement within the first 50 miles, then every 3 hours or 150 miles, whichever comes first, and after every break.
