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.