Proposal to establish a new UN Regulation transposing UN GTR No. 24 into uniform provisions concerning approval of non-original and identical replacement brake parts (brake pads, drum brake linings, brake discs, and brake drums) with regards to particle emissions. The regulation applies to vehicles of category M₁, N₁, and N₂ between 3.5 and 5 tonnes maximum mass. Replacement brake parts must comply with particle emission limits, with emission factors calculated using test wheel load and friction braking share coefficient for the brake emissions family parent. Approval marks must be affixed to approved parts, and conformity of production shall be verified through sampling and testing procedures.

UN R13 and UN R78 establish different brake system requirements for 4-wheel vehicles. R13H requires split service brake systems with front/rear proportioning; R78 permits split service brake systems, combined brake systems, or two separate service brake systems without proportioning requirements. Type-O dry braking tests differ: R13H requires engine disconnected at 100 km/h with stopping distance 0.1v + 0.0060 v² and MFDD 6.43 m/s²; R78 specifies multiple tests at 40, 60, and 100 km/h with varying requirements. Type-I brake fade tests use different snub protocols and performance thresholds. Secondary braking failure criteria differ at specified speeds. R78 requires wet brake testing, a 30 km/h dynamic park brake test with 18% gradient and 5 minutes hold time; R13H specifies static gradient tests. R78 includes detailed ABS, functional safety, and regenerative braking requirements; R13H does not.