In my area, “monster” pick-up trucks and 4-wheel drives are common. Quite often these trucks are raised so high that even with an open bed, the contents are not visible. To avoid being surprised by unseen passengers or dogs riding in the back of raised pick-ups, carefully observe the bed before stopping the vehicle and making your approach. Once it’s stopped, look carefully for signs of movement, and if the walls of the bed are above eye level, change your angle of approach so you’re not walking alongside the truck bed while walking up.