you can go down a mountain slow a hundred times, but you might only go down it once fast!

two times ago in Oregon I saw where a truck went through the gaurd rail up on cabbage pass, way up on the hill right where you get the panoramic view of pendelton. the truck went down the side 3 hundred yards and both drivers survived. well they had to be extracted before they limped away.
actually I think riding a bike helps prepare you to drive truck, you have similar goals like;
not running over the 4 wheelers/cagers in a truck/ and not being run over by them on the bike
the challenge for both vehicles is not going straight down a road ( steering wheel holder ) its in close quarters manuevering and also backing up in a truck.