| UN R55 Mechanical Couplings | Mechanical Coupling Components | Uniform provisions concerning the approval of mechanical coupling components of combinations of vehicles Mechanical Couplings Mechanical Coupling Components UN Regulation No. 55 UN R55 | UNR | 55 | |
| UN R13 Heavy-Duty Braking | Heavy-Duty Vehicle Braking | Uniform Provisions Concerning the Approval of Vehicles of Categories M, N and O with regard to Braking Heavy-Duty Braking Heavy-Duty Vehicle Braking UN Regulation No. 13 UN R13 | UNR | 13 |