The 15th RD-ASEP informal group session will be held at Nissan Technical Center Europe Spain in Barcelona. The venue is located 11 minutes walk from Mercabarna Metro Station Line 9S. Participants should make hotel reservations independently; options include areas near metro line L9S or city center near metro line L5, which connects with L9S. Participants must provide last name, first name, phone number, company name, and email in advance.

Proposal to amend UN Regulation No. 51 on the noise of M and N category vehicles, introducing comprehensive provisions for measuring and limiting sound emissions. The proposal establishes testing methods for vehicles in motion and at rest, defines sound level limits by vehicle category and power characteristics, and introduces Real Driving Additional Sound Emission Provisions (RD-ASEP) for M1 and N1 vehicles to ensure compliance during typical on-road driving conditions representative of urban and suburban traffic. Transitional provisions permit Contracting Parties to continue approving vehicles under preceding series until a specified date.

Proposal to establish revised terms of reference for the IWG RD-ASEP covering vehicles of categories M₁, N₁, and L₃. The group shall modify current regulations to mandate revised RD-ASEP, update Annex 9, delete Annex 7 and update relevant paragraphs in the main body and Annex 3 of UN R51, develop limit curves for different riding situations in UN R41-05, consider relevant transitional provisions, and develop coordination between UN R51 and UN R138. The IWG shall be chaired by Germany with OICA as Secretary for M/N categories and IMMA for L category, and shall present a working document for M₁ and N₁ vehicles by February 2028.

Document presents comparison of UN R51.03 ASEP, UN R51.04 RD-ASEP, and an updated ASEP alternative concept. It outlines improvements including explicit testing of all conditions to reduce test detection schemes, expanded vehicle speed range to 1-100 km/h, random test point evaluation, and extension to part load conditions. Main open topics include tyre model stability, technology and model temperature correction, application and uncertainties, and criteria and judgement safeguards. Document identifies quick wins through clarification that all modes must be tested and suggests main improvements can be realized through an updated, simple ASEP with part load testing capabilities.