This International Standard specifies the test procedures for testing the operational performance requirements of towed vehicles of Category O (full trailers, semi-trailers, and centre-axle trailers) as defined in Annex 7 of the UN-ECE Consolidated Resolution on the Construction of Vehicles (R. E. 3). This includes vehicles fitted with compressed air braking systems (with and without an antilock braking system or an electronically controlled braking system), in accordance with UN-ECE Regulation No. 13, 09 series of amendments, supplements 1 to 6. Test methods covering lock actuators are not included. The values in square brackets [ ] and the values in the tables are taken from ECE Regulation No. 13 for information.