Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p22
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 22/108)
Character Range: 945521–948614

j, if applicable, m²;

                     ρ0 is the dry air density defined in paragraph 3.2.10. of this Regulation, kg/m³;

              vj is the reference speed j, km/h.

              6.7.3. Calculation of road load values

              The total road load as a sum of the results of paragraphs 6.7.1 and 6.7.2. of this annex shall be calculated using the following equation:

              for all applicable reference speed points j, N.

              For all calculated  , the coefficients f0, f1 and f2 in the road load equation shall be calculated with a least squares regression analysis and shall be used as the target coefficients in paragraph 8.1.1. of this annex.

              In the case that the vehicle tested according to the wind tunnel method is representative of a road load matrix family vehicle, the coefficient f1 shall be set to zero and the coefficients f0 and f2 shall be recalculated with a least squares regression analysis.

              6.8. Road load delta method

              For the purpose of including options when using the interpolation method which are not incorporated in the road load interpolation (i.e. aerodynamics, rolling resistance and mass), a delta in vehicle friction may be measured by the road load delta method (e.g. friction difference between brake systems). The following steps shall be performed:

                  (a) The friction of reference vehicle R shall be measured;

                  (b) The friction of the vehicle with the option (vehicle N) causing the difference in friction shall be measured;

                  (c) The difference shall be calculated according to paragraph 6.8.1. of this annex.

              These measurements shall be performed on a flat belt according to paragraph 6.5. of this annex or on a chassis dynamometer according to paragraph 6.6. of this annex, and the correction of the results (excluding aerodynamic force) calculated according to paragraph 6.7.1. of this annex.

              The application of this method is permitted only if the following criterion is fulfilled:

              where:

                  FDj,R is the corrected resistance of vehicle R measured on the flat belt or chassis dynamometer at reference speed j calculated according to paragraph 6.7.1. of this annex, N;

                  FDj,N is the corrected resistance of vehicle N measured on the flat belt or chassis dynamometer at reference speed j calculated according to paragraph 6.7.1. of this annex, N;

              n is the total number of speed points.

              This alternative road load determination method may only be applied if vehicles R and N have identical aerodynamic resistance and if the measured delta appropriately covers the entire influence on the vehicle's energy consumption. This method shall not be applied if the overall accuracy of the absolute road load of vehicle N is compromised in any way.

              6.8.1. Determination of delta flat belt or chassis dynamometer coefficients

              The delta road load shall be calculated using the following equation: