Like the ones that you quoted on French lorries, you forgot 60 by the way, these are for their own countries and nothing to do with the countries that they are visiting.
For example, the French ones:- 90 is Autoroutes, (which you may have noticed will have a closed HAZCHEM plate by it), because if you’re carrying hazardous you open it up and it covers the 90 as the limit is lowered to 80 which is in fact the limit for National/Departmental roads, single and dual carriageway. The 60 is for non priority routes ( yellow diamond with a line through it) static.passetoncode.fr/img-panne … es/ab7.jpg.
Within towns limits it is 50kph.
