RD-ASEP includes technical background and vehicle application guidance for Real Driving Additional Sound Emission Provisions under UN R51.03 Supplement 7 Annex 9 for the mandatory monitoring phase between 07/2023 and 06/2024. RD-ASEP, referenced in GRB-68-03, applies to vehicles of category M₁ and N₁ equipped with internal combustion engines and covers engine speeds up to 95% of typical driving in speed ranges applicable to sub-urban conditions. A Sound Expectation Model predicts vehicle sound levels at randomly selected operation conditions by splitting measured pass-by test results into tyre rolling sound, mechanical no-load sound, and dynamic sound components, using reference values from Annex 3 type approval tests with logarithmic functions and parameter table slopes. Compliance assessment allows measured sound to exceed calculated expected sound by not more than 2 dB for maximum two test runs out of fifteen. Model validation with 2024 monitoring database confirms the tyre rolling sound and power train sound models represent well approved tyres and engines, with less than 5 dB typically separating pass-by run results from the limit.

An improvement intended to increase vehicle robustness in Annex 3 creates more difficulties in RD-ASEP assessment. Small variations in Annex 3 parameters may result in unexpected substantial exceedances in Annex 7. Minimal changes in the calculated tyre share at the anchor point may cause vehicles to fail Annex 7. The regulation should ensure realistic test effort and workload for compliance verification, as current requirements may require up to 180 combinations per type across test tracks, temperatures, driving modes, and tyres.

The IWG RD-ASEP is developing a mandatory test procedure to assess compliance with paragraph 6.2.3 of UN R51.04, ensuring vehicle noise emissions at various speed, load, and acceleration conditions are linked to vehicle physics without defeat devices. R51.04 RD-ASEP expands testing from full acceleration only to any acceleration position, increases vehicle speed range from 20–80 km/h to 1–100 km/h, adds vehicle performance criteria, requires random test points for approval rather than manufacturer declaration, and can test gears and loads previously unavailable. An updated GRB-68-03 will accompany R51.04. Submission targets include informal draft September 2026 and expected working document adoption February 2028, with TOR extension requested through 2028.