Every packed container that leaves the UK by sea now travels with a number it did not always need: a verified gross mass - the VGM - declared before the box can be loaded onto a ship. The requirement came out of the SOLAS safety convention after too many misdeclared weights destabilised stowage plans, broke lifting gear and, at the sharp end, contributed to casualties. The government’s guidance on verification of gross mass, built around the Maritime and Coastguard Agency’s Marine Guidance Note 534, sets out how the UK applies it - and it reaches further up the logistics chain than the shipping line, touching every haulier who delivers boxes to port.
The principle is simple: the packed container’s weight must be verified - actually determined by an approved method, not estimated or copied from the booking - and the verified figure must reach the ship and terminal in time for stowage planning. No VGM, no loading: a container arriving at the terminal without one does not sail, and the costs and delay of that refusal land back up the chain on whoever failed to supply the number. The guidance points to MGN 534 for the detail, and it covers the two routes the rules allow for getting the verified weight.
Method 1 is direct weighing: weigh the packed and sealed container, whole, on calibrated equipment - a weighbridge, weighbridge-style terminal equipment, or approved lifting-device weighing. It is the simplest conceptually and the answer for many shippers: the loaded box goes over a weighbridge and the number goes on the declaration.
Method 2 is calculation: weigh everything that goes into the container - the cargo items, packaging, dunnage, securing material - and add the container’s own tare weight to produce the total. Method 2 suits shippers with controlled packing operations and weighing built into their process; it demands a methodology the shipper can defend, because the figure is constructed rather than measured. The guidance notes that the MCA approves container-weighing methods, and it maintains a public database of MCA-approved weighers - the reference for anyone needing a Method 1 weigh who does not own a weighbridge.
Either way, the weight is declared as the VGM on the shipping documentation, signed off by the shipper named on the bill of lading - and “shipper” here is the party on the document, which in freight-forwarded chains is sometimes three removes from the person who physically packed the box.
Road carriers sit in the middle of the VGM chain without being the declarant, and the position creates its own disciplines. First, know what the job assumes: is the customer providing the VGM from their own Method 2 calculation, or does the booking expect the haulier to get the box weighed? A truck turned away at the terminal for a missing VGM is a wasted journey and an awkward invoice - the booking conversation should establish whose number it is before the collection is dispatched.
Second, the weighbridge visit is real work. Method 1 weighing on the way to port means a calibrated weighbridge, the time to use it, and the document trail - and the truck’s own weight becomes part of the calculation when a container is weighed on the vehicle, so the routine has to be right. Third, the gross mass is also a legal weight question for the road leg: a VGM that reveals a container heavier than the truck’s plated capacity is not just a shipping problem, and the haulier who notices is doing everyone a favour.
The VGM rules arrived amid predictions of chaos - boxes refused at gates, terminals gridlocked, shippers unable to weigh. What actually happened was quieter: the chain absorbed the requirement into its paperwork, weighbridges and terminal systems did the weighing where shippers could not, and the database of approved weighers filled the gaps. The lesson the episode left behind is the one worth keeping: the safety of the whole stow depends on a number that originates with someone who packs a box in a warehouse - and the system only works because every link, including the haulier, treats that number as a fact to be produced rather than a detail to be assumed.
The VGM regime also had a quieter side effect that the industry now takes for granted: it normalised weighing. Before the rule, plenty of containers moved on estimated weights and everyone accepted the imprecision; after it, calibrated weighing became an unremarkable part of the export routine, and the data discipline spread into adjacent areas - load planning, axle-weight checking, and the general expectation that a declared weight is a measured weight. For a road sector that has always lived with overloading risk, that cultural shift is worth as much as the shipping safety it was designed for: once weighing becomes normal, guessing becomes the anomaly.