What does stgo cat2 mean?

special type group order,

means they can work above the 44 tonne limit for HGVs/LGVs in the UK, there are quite strict rules of using this category of vehicles if carrying abnormal (both size and/or weight) loads.

they ave to use certain routes and inform the police of their planned movements and sometimes are only allowed to move at certain times to minimise disruption to joe public!