Don't ever be fooled by "I have things secured in the bed". It's a rookie mistake, and even a vet can get surprised. I've seen destruction and I've experienced destruction. Exploding cans, burst gas jugs, chase racks coming loose, tires breaking free, tool boxes shattered, power tanks getting sheared nozzles, axes and shovels bouncing around, etc. Pull over frequently and check things out.
You might even have things nice and tight and secure, but then the tie-down strap snaps. My buddy had a two inch heavy duty strap pull apart like it was Christmas ribbon. They weren't aged or worn, they were a week old.
Lecture over! Have a great trip and stay safe!