I did some agency driving there for a week and learnt something they don't tell you in your HGV test... Coal dust is VERY slippery when wet.
I drove my eight wheel tipper straight in to the back of another one. There I was, a good 300 metres from the truck in front... A little bit of gentle breaking... WTF!!!! Nothing's happening... Try a bit of cadence breaking... Nope... Try whacking the fucker in reverse and giving it full throttle... ARRRRGH!!! CRUNCH!!!
"Don't worry about it mate" says the driver in front "We all do that at least once a month that's why all of the trucks have their fronts smashed in"