S.L. 65.21 ст. 5Classification of trailers.

Trailers shall be classified as follows:

CATEGORY O

Trailers (including semi-trailers)

- O1 - Trailers with a maximum mass not exceeding 0.75 tonnes; - O2 - Trailers with a maximum mass exceeding 0.75 tonnes but not exceeding 3.5 tonnes; - O3 - Trailers with a maximum mass exceeding 3.5 tonnes but not exceeding 10 tonnes; - O4 - Trailers with a maximum mass exceeding 10 tonnes.

In the case of a semi-trailer or centre-axle trailer, the maximum mass to be considered for classifying the trailer corresponds to the static vertical load transmitted to the ground by the axle or axles of the semi-trailer or centre-axle trailer when coupled to the towing vehicle and carrying its maximum load.