There are several weights for a single vehicle<div abp="1301">
<div abp="1302">Unladen Weight = Dry Weight = no fuel, water, driver and for EV, batteries ( useful for shipping calculations
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<div abp="1304">Kerb Weight = Car + fuel, water, standard tools & spare, driver of 75 Kg( I wish
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<div abp="1304">Gross Vehicle Weight = Maximum Authorised Mass = Kerb Weight+ Passengers/cargo.
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<div abp="1304">Gross Train Weight = Maximum weight of vehicle and trailer combined.
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<div abp="1304">This last one is a curates egg. The weight of the trailer has to be its maximum plated weight irrespective of its actual load. People have been prosecuted for towing an empty car trailer because the towing vehicle could not have legally towed it if fully laden.
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<div abp="1304">However the car does not need to be considered at anything other than the rolling weight.
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<div abp="1304">The 80Kg discrepancy comes about because the vehicle could be at its Kerb weight or GVW. As that difference is even more than the rated weight then engineering limits are in effect.
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<div abp="1304">At below 750Kg the trailer is unbraked which makes a massive difference to the loading conditions for the towbar so easier to design.At 1/4 of the GVW there is a low engine load consideration to make although there is a change for the 1.0L
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<div abp="1304">So it can take 480Kg unless fully laden when it drops to 400Kg. The driver is always responsible to ensure that the train is properly loaded.