RE: Gross vehicle weight
I wouldn't expect the dump to have a split scale though, for that the better place is some kind of truck stop. I'm not sure what they use in Belgium, or even what their name for it is, but most any kind of heavy truck driver there should be able to point him in the correct direction.
The reason I am recommending the split scale if at all possible is that will give some idea of load distribution which affects handling during stopping.
If the rear is much heavier than the front there is a tendency for it to come around in a quick stopping scenario. Which on any type of slick surface is a nasty thing to have, because not only do you loose traction (slick), but control(sideways).
You may notice that heavy tractor trailers have a method for brining the
rear wheels forward or even spreading the rear set apart to distribute the weight better. Split scales for tractor trailers have 3 sections usually,
This is also the reason when the aprotioning valve is working properly that more of the brake preasure is applied to the rear brakes even though approximately 70% of the stopping power is on the front wheels.