Health and safety can come down to the site and make life very bothersome for them! I agree the law is already there, they make some farmers take water tanks with them, they don't bother much with lanes, but A roads and motorways they take it seriously. Highways agency maybe better than police.
I had 2 windscreens done when they built the rail link, never got to the lorries as going the other way. I spoke to some on site, they all knew they were illegally over loaded and not secured/covered, but the pressure was on to shift as much as possible quick. They would rather pay out for the damage, than run more trucks (actually cheaper). I am talking about the full load being not visible, but you can put an extra 5-10 ton in and not notice on the modern vehicles unless they get weighed! (or you can see a pile of stone from the road mounded above the top of the trailer!!)!
Mud also, they used to wash the undercarriage because they had too for the roads.