3. For the definition of “converter dolly” in the Table in regulation 3(2) there shall be substituted—
“(a)a trailer which is—
(i)equipped with 2 or more wheels,
(ii)designed to be used in combination with a semi-trailer without any part of the weight of the semi-trailer being borne by the drawing vehicle, and
(iii)not itself a part either of the semi-trailer or the drawing vehicle when being so used; or
(b)a trailer which is—
(i)equipped with 2 or more wheels;
(ii)designed to be used in combination with a semi-trailer with part of the weight of the semi-trailer being borne by the drawing vehicle;
(iii)not itself a part either of the semi-trailer or the drawing vehicle when being so used; and
(iv)used solely for the purposes of agriculture, horticulture or forestry, or for any two or for all of those purposes.”