The damned instructions are printed on the Bowser anyway for all to see!
On the back of my truck is a large sign, "Only driver to operate controls" It would blow your mind how often the customers start fiddling with stuff.
How often do you goto a servo and see people refueling whilst on the phone? The official line is its a flash hazard....a dumbed down explanation to scare the masses. The real reason, is they want you to concentrate on what you are doing.
And what IFEZ says about a course and fee......its coming. I have to demonstrate once a month to my managers that i know how to enter and exit my truck safely...am actually tested. FFS!