Summary of the Task Force Data Analysis meeting held 29 September 2026. The meeting discussed amendments to factor x for improved model robustness, consideration on LDYN with amendments on factor x, and considerations on the AVAS term to match UN R138. Proposals to the TF-Editing were discussed based on draft UN R51.04, including input from Germany. The Editing TF raised a question regarding the phrase “but no more than 2.0 m/s” in para. 3.1.2.1.4.3 concerning vehicles with only one gear ratio, which was included in Supplement 11 to UN R51.03 to prevent unrealistic kp values. TF-DA suggested proceeding with the adopted text as is.

Proposal to amend Annex 7, paragraph 2.3.1 to explicitly frame the area of valid values for factor x, requiring that the factor x determined by measurements shall always be at least 0.10 and not exceed the values provided by the parameter table in Appendix 2 to that Annex. The document explains that factor x is used to split constant speed test results energetically into tyre rolling sound and power train mechanic references, and that measurement variations can cause significant variability in calculated values, particularly when factor x exceeds 0.90.

Agenda for the Task Force Data Analysis meeting of 29 September 2026. Discussion topics include amendments to factor x for improved model robustness, consideration on LDYN with amendments on factor x, considerations on the AVAS term to match UN R138, amendments to reference acceleration, temperature correction, indoor testing, simplified model for electric vehicles with integrated AVAS approach and amendments from Supplement 11, and considerations on slopes in the RD-ASEP model. The Task Force will prepare proposals for wording on issues identified in the editing task force list and address a clarification request regarding the phrase ‘but no more than 2.0 m/s’ in para. 3.1.2.1.4.3. concerning vehicles with only one gear ratio.

Proposal to amend Annex 7, para. 2.3.1 to constrain the factor x determined by discrete coast-down measurement to a minimum of 10 and a maximum of 90 for internal combustion engine and hybrid electric vehicles, or 95 for electric vehicles, ensuring the Sound Expectation Model remains robust against measurement variations in tyre rolling sound and powertrain mechanic sound splitting.

Document presents considerations on amendments to the RD-ASEP Sound Expectation Model SEM concerning calculation of the dynamic base and dynamic load addon. The dynamic sound increase of a vehicle is covered by a dynamic term aggregating all dynamics. A minimum threshold is proposed to be specified as max(0.25; ΔL_dyn) to ensure the function does not become zero or negative due to measurement uncertainties. The value 0.25 is selected to deliver comparable results as the current 10 dB minimum dynamic specification. In combination with a restriction of factor x to an area of 10 to 90 for ICE, the model becomes very robust with fluent transients and no unsteady steps.