There are four triggers, and only one of them has to apply: width, height, length, or weight. Exceed the standard legal limit on any single one and the load needs authorisation before it can travel.
Height is the trigger that surprises people most often. Cargo measured on the ground can sit comfortably inside the limit and still be over once it is on a trailer deck — which is exactly why the deck height of a lowbed matters so much for tall machinery.
Weight has its own subtlety: it is not only the total that counts but how that total lands on each axle. A compact, dense unit can breach axle limits while sitting well inside the trailer's rated capacity.
The practical answer: send us the length, width, height, and weight, and we will confirm whether your load needs a permit, an escort, or both — before you commit to a date.