Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p6
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 6/108)
Character Range: 900072–903226

less than + 5 km/h (to avoid conditions where tailwind speed is higher than vehicle speed) shall also be flagged. Data analysis shall be restricted to vehicle speeds within the speed range selected according to paragraph 4.3.2.2. of this annex.
              4.3.2.6.7. Final data analysis
All data that has not been flagged shall be analysed using a linear least squares regression technique. GivenAm, Bm, Cm, a0, a1, a2, a3 and a4 shall be determined.
              4.3.2.6.8. Constrained analysis (optional)
              To better separate the vehicle aerodynamic and mechanical drag, a constrained analysis may be applied such that the vehicle's frontal area  and the drag coefficient CD may be fixed if they have been previously determined.
              4.3.2.6.9. Correction to reference conditions
              Equations of motion shall be corrected to reference conditions as specified in paragraph 4.5. of this annex.
              4.3.2.6.10. Statistical criteria for on-board anemometry
              The exclusion of each single pair of coastdown runs shall change the calculated road load for each coastdown reference speed  less than the convergence requirement, for all and :
              where:
                    is the difference between the calculated road load with all coastdown runs and the calculated road load with the ith pair of coastdown runs excluded, N;
                    is the calculated road load with all coastdown runs included, N;
                    is the reference speed, km/h;
                   n is the number of pairs of coastdown runs, all valid pairs are included.
              In the case that the convergence requirement is not met, pairs shall be removed from the analysis, starting with the pair giving the highest change in calculated road load, until the convergence requirement is met, as long as a minimum of 5 valid pairs are used for the final road load determination.
              4.4. Measurement and calculation of running resistance using the torque meter method
              As an alternative to the coastdown methods, the torque meter method may also be used in which the running resistance is determined by measuring wheel torque on the driven wheels at the reference speed points for time periods of at least 5 seconds.
              4.4.1. Installation of torque meters
              Wheel torque meters shall be installed between the wheel hub and the wheel of each driven wheel, measuring the required torque to keep the vehicle at a constant speed.
              The torque meter shall be calibrated on a regular basis, at least once a year, traceable to national or international standards, in order to meet the required accuracy and precision.
              4.4.2. Procedure and data sampling
              4.4.2.1. Selection of reference speeds for running resistance curve determination
              Reference speed points for running resistance determination shall be selected according to paragraph 2.2. of this annex.
              The reference speeds shall be measured in descending order. At the request of the manufacturer, there may be stabilization periods between