each trailer category described in points 11 to 14 is supplemented at the end by an ‘a’ or ‘b’ index, according to its design speed:
déantar gach leantóra a thuairiscítear i bpointe 11 go pointe 14 a fhorlíonadh ag an deireadh le hinnéacs “a” nó “b” de réir a luas dearaidh: