Proposal to simplify the RD-ASEP SEM assessment method for electric vehicles using the Supplement 11 to UN R51 slope assessment approach, limit factor x between 0.10 and 0.95, apply AVAS as a uniform 66 dB(A) maximum up to 50 km/h, and replace the existing SEM-AVAS term with this revised strategy. The tyre rolling sound curve, acceleration term from UN R51.03 Supplement 11, and AVAS term aligned with UN R138 are applied, while no other SEM parts are used.

Notes from the 19th meeting of the Task Force Data Analysis, a sub-group of IWG RD-ASEP, scheduled for 2 November 2026. The meeting will discuss amendments to RD-ASEP including treatment of AVAS as a component, consideration of L_DYN definitions, a simplified assessment method for electric vehicles, rounding procedures, and temperature correction. Open items for TF-Editing include independence of test points, gear-shifting and HEV engine operation, dynamic jump, and low load cruising acceleration determination.

Draft agenda for the nineteenth meeting of the Task Force Data Analysis, a subgroup to IWG RD-ASEP, scheduled for 2 November 2026. The meeting will address continued discussion on amendments to RD-ASEP, including consideration of LDYN definition, simplified assessment methods for EV, rounding procedures, and temperature correction. Open items concern independence of RD-ASEP test points correlation assessment, gearshifting and HEV engine operation, dynamic jump, and low load cruising acceleration determination.

Proposal to simplify the RD-ASEP Sound Emission Model for electric vehicles by using the tyre rolling sound curve with factor x set to 1.00 and slopes from the SEM parameter table, adopting the acceleration term from UN R51.03 Supplement 11, aligning the AVAS term with UN R138 as a uniform value of 66 dB(A) maximum sound up to 50 km/h, limiting factor between 0.10 and 0.90, using LDYN as specified, and replacing the existing SEM-AVAS term with the new strategy.

Overview of rounding principles for calculations in models where results are used for further calculation. Recommends carrying full precision until the end and applying rounding only to final output. Identifies Round Half to Even as standard for modeling and statistics, and Round Half Up as used in UN Regulations. Advises matching output precision to input data uncertainty and not reporting more precision than input data warrants.

Task Force Data Analysis provides input to the Editing Task Force on three items. For vehicles with single gear ratios, remove brackets from text restricting acceleration to no more than 2.0 m/s and continue with adopted text for UN R51.04. Restructure Annex 7 paragraph 4.4. into subparagraphs for clarity. Rework paragraph 3.6.1. to define reference acceleration with v-t-e ratio and specify procedures for determining maximum reference acceleration. Add specification to factor x determination to prevent extreme results and harmonize its representation as either percentage or decimal value.

Report from the Task Force Data Analysis to the Informal Working Group on Real Driving Sound Emissions and Performance (IWG RD-ASEP) covering several technical matters: clarification on restrictions in UN R51 supplement 11 to avoid high noise levels for single-gear vehicles; restructuring of control range specifications in Annex 7; redefinition of maximum reference acceleration for the sound emission model; discretization of factor x determination with consideration of rounding procedures; clarification of AVAS sound level requirements distinguishing between whole-vehicle and component-level interpretations; and temperature correction application for the sound emission model. Further work topics include indoor testing, EV model simplification, and slope considerations.

Proposal to replace the current logarithmic function with a segmented function that linearizes the curve in the unstable area near the clipping boundary. The new formulation uses a tangent line to the logarithmic curve below the tangency point and clips to a minimum value of 10 dB. Two parameters define the tangency and clipping conditions: clipping value of 10 dB and slope of 5 dB per unit. The detailed formulation provides the mathematical definitions of the logarithmic function, the linearized segment, helper variables, and constraints including tangency and asymptote conditions.

Agenda for the 18th meeting of the Task Force Data Analysis, a sub-group to IWG RD-ASEP. The meeting will review and adopt the agenda, discuss the meeting schedule for November and December 2026, continue discussion on necessary amendments to RD-ASEP including LDYN definition, AVAS term alignment with UN R138, temperature correction, indoor testing, simplified EV model with integrated AVAS approach and Supplement 11 amendments, and slopes and parameter table settings. The meeting will review proposals to the TF-Editing and decisions for the next meeting.

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.

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.

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.

Considerations by TF Data Analysis on revising the AVAS term in the RD-ASEP Sound Expectation Model to align with UN R138.02 specifications for electric and hybrid electric vehicles. The document presents two options: Option 1 implements UN R138.02 specifications for constant speed conditions; Option 2 extends Option 1 with an additional term to reflect paragraph 6.2.8 requirements for accelerated conditions. A revised AVAS term formula is proposed applicable only for vehicle speeds up to 50 km/h.

Proposal to restructure para. 4.4. by dividing it into paras. 4.4.1. through 4.4.8., add a new para. 4.4.7. permitting acceptance of measurements of RD-ASEP leading to operation conditions outside the control range when agreed by the manufacturer and authority, modify the heading of para. 3.6.1. to reference a selected reference v-t-e ratio, update references to v-t-e ratio terminology throughout para. 3.6.1.1., add a provision that negative acceleration values be set to zero in para. 4.5.4.1., restructure para. 2.2.1.2. by renumbering into paras. 2.2.1.2.1. and 2.2.1.2.2., and modify the reference vehicle speed parameter designation from vTEST to vPP,CRS.

Document presents considerations on factor x used in the Sound Expectation Model to split constant speed test results into tyre rolling sound and power train mechanic references. Factor x values are concentrated between 80 and 99, indicating tyre dominance. Small variations in measurements cause disproportional variability in the minor sound source when one source dominates. Two options are proposed: Option 1 requires factor x determined during type approval to be reported and used for subsequent assessments, with any redetermination not exceeding the type approval value; Option 2 requires the power train reference from type approval to be used for all further assessments regardless of measurement variations.

Proposal to amend the determination of reference acceleration aREF by introducing a theoretical calculation formula based on PMR, rated engine speed S, and vehicle mass mro, with a correction function accounting for transmission losses, virtual mass increase, tyre slip, and turbo delay, and to allow manufacturers to alternatively determine reference acceleration by discrete measurements.