In the catalogue, the weight of a NAVY RIB is an empty weight: the NAVY 4.80 weighs 300 kg, the NAVY 6.00 600 kg, the NAVY 7.60 800 kg. For the NAVY 5.50, the NAVY 6.60 and the NAVY 9.50 Cabin we give you the weight on request, together with the quote. These figures help you grasp the order of magnitude; they do not settle the sum for the road.
The sum for the road is done on paper. The licence does not look at how much the boat weighs: it looks at the maximum authorised mass of the trailer and of the combination, that is car plus trailer, written on the registration documents. The trailer has to carry the RIB with everything that travels on board: the engine on the transom, the fuel in the tank, which holds 60 litres on the NAVY 4.80 and 280 on the NAVY 7.60, the gear in the lockers. And the trailer itself has a weight, which counts towards the mass of the trailer.
Under the Italian Highway Code a RIB trailer is a trailer in every respect. Art. 56, paragraph 2, letter f), calls it a trailer for carrying tourist and sporting equipment: single-axle, or with two axles no more than one metre apart, fitted with the specific equipment for carrying, among other things, boats. It is not to be confused with the luggage trailer, which paragraph 4 of the same article treats as part of the vehicle that tows it.
Art. 62 also sets the mass limits for any fully laden vehicle: 5 tonnes on a single axle, 8 on two axles. For anyone towing a RIB, though, the limit you meet first is the licence one, read from the maximum authorised masses on the registration documents.