Your braking and acceleration will be the thing they look at the most along with putting on the park brake when you come to a stop or keeping your foot brake on. This is because if you’re taking liquid in a tanker, especially milk where the tanks can’t be baffled, the liquid moves more when you come to a stop or accelerate harshly and when you come to a stop if you don’t either put the park brake on or keep your foot brake applied the movement of the liquid can be enough to push you forward. Also you need to let the vehicle in front of you move off a bit further than normal before you set off because if you time it wrong so you’re letting off the brake as the surging liquid reaches its forward most point of movement the moment you let off your brake you can shoot forward very quickly.