IWG RD-ASEP is developing a mandatory test to assess compliance with paragraph 6.2.3 of Regulation 51.04 main body, assuring vehicle noise emission at speed, load, or acceleration conditions other than Annex 3 condition is linked to vehicle physics with no noise emission test detection or defeat device schemes. After the 13th session in June 2026, the Editing Task Force created a consolidated R51.04 draft incorporating R51.03 Supplements up to Supplement 11, with mandatory random RD-ASEP testing for approval and revised control range. Submission targets include informal document first draft September 2026, second draft February 2027, and expected working document for adoption February 2028.

This document presents a clean draft proposal for the 04 series of amendments to UN R51 (Noise of M₁–M₃ and N₁–N₃ Categories of Vehicles). The proposal establishes uniform provisions for sound emission approval of motor vehicles with at least four wheels, introducing comprehensive specifications for measuring vehicle noise during motion and stationary conditions. Key provisions include detailed test methods with outdoor and indoor testing options, sound level limits varying by vehicle category and power characteristics, requirements for vehicles of categories M₁ and N₁ to comply with Real Driving Additional Sound Emission Provisions (RD-ASEP), specifications for exhaust silencing systems containing fibrous materials, conformity of production procedures, and specific adaptations for vehicles equipped with Automated Driving Systems. The regulation applies from its official entry into force, with a transitional period allowing acceptance of prior-series approvals until a specified date.

Proposal to amend Annex 3 and Annex 7 regarding ASEP calculations and temperature corrections:

• Add reference to nMAX and kp factor for ASEP anchor point calculation in Annex 3, Appendix 1 Table 1,
• Clarify temperature correction equations and coefficients K1 and K2 by defining them uniquely in para. 3.2.3. and adding missing index j references in Annex 3, Appendix 2 paras. 3.2.3., 3.2.4., 3.3.3. and 3.3.4.,
• Delete from Annex 7 para. 5.2. a sentence regarding gear ratios for ASEP Lref that was wrongly introduced in Supplement 10 (GRBP-79-33/Rev.1).