The four sub-categories
Classification depends only on maximum technically permissible mass:
- O1: up to 750 kg — bike trailers, small luggage trailers, garden trailers;
- O2: 750 kg to 3,500 kg — caravans, car transporters, site trailers;
- O3: 3,500 kg to 10 tonnes;
- O4: above 10 tonnes — semi-trailers and industrial trailers.
Crossing 750 kg also changes the engineering: above it the trailer must be braked, and the licence needed depends on the combined gross masses of vehicle and trailer.
When must a trailer be registered?
In France a trailer whose gross mass exceeds 500 kg needs its own registration certificate. Below that it carries the towing vehicle’s plate and needs no registration — but it still has to be type-approved.
For a trailer bought elsewhere in the EU, the COC supplies the masses, dimensions and approval number the file needs. Without it, the authority cannot fill in the registration certificate.
Caravans: the masses that matter
Two figures count on a caravan: mass in running order and gross mass. The difference is what you can load, equipment included. Manufacturers often offer an approved gross-mass upgrade: it must appear on the document, otherwise it does not exist administratively.
Nose weight is also stated: exceeding what the towing vehicle’s towbar allows is a common cause of non-compliance.
Trailer approval in Europe
Every trailer placed on the EU market must be approved; European trailer approval has been effective since the early 2010s. A home-built trailer has no approval and cannot obtain a COC: it goes through an individual approval instead.