Japan comments on the draft 04 series of amendments to UN R51 (Noise of M₁–M₃ and N₁–N₃ Categories of Vehicles). Japan highlights several editorial and technical issues. Regarding para. 2.24.1, Japan suggests the table of symbols for Annex 3 should state symbols are “used for the first time” consistent with ISO standards. For para. 3.1.2.1.4.3, Japan requests deletion of “but no more than 2.0 m/s²” as unnecessary for RD-ASEP applied to electric vehicles. Japan notes para. 6.2.3.4 should reference appropriate appendices for the RD-ASEP statement of compliance requirement. Paragraphs 11.1.4 and 11.1.5 are identical and one should be deleted. Japan flags para. 3.2.3.4.2 requires tyre conditioning on outdoor test tracks for indoor testing. For Annex 6, para. 3 should clarify that compliance assessment references para. 5 of Annex 7 for expected sound pressure level limits applicable to conformity of production testing.