Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p14
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 14/108)
Character Range: 922704–925835

road load based on vehicle parameters
              5.2.1. As an alternative for determining road load with the coastdown or torque meter method, a calculation method for default road load may be used.
              For the calculation of a default road load based on vehicle parameters, several parameters such as test mass, width and height of the vehicle shall be used. The default road load Fc shall be calculated for the reference speed points.
              5.2.2. The default road load force shall be calculated using the following equation:
            where:
                   Fc is the calculated default road load force as a function of vehicle velocity, N;
                   f0 is the constant road load coefficient, N, defined by the following equation:
              ;
                   f1 is the first order road load coefficient, N/(km/h), and shall be set to zero;
                   f2 is the second order road load coefficient, N/(km/h)2, defined by the following equation:
                 ;
                   v is vehicle velocity, km/h;
                   TM test mass, kg;
                   width vehicle width as defined in term No. 6.2. of Standard ISO 612:1978, m;
                   height vehicle height as defined in term No. 6.3. of Standard ISO 612:1978, m.
              6. Wind tunnel method

              The wind tunnel method is a road load measurement method using a combination of a wind tunnel and a chassis dynamometer or of a wind tunnel and a flat belt dynamometer. The test benches may be separate facilities or integrated with one another.

              6.1. Measurement method

              6.1.1. The road load shall be determined by:

                  (a) Adding the road load forces measured in a wind tunnel and those measured using a flat belt dynamometer; or

                  (b) Adding the road load forces measured in a wind tunnel and those measured on a chassis dynamometer.

              6.1.2. Aerodynamic drag shall be measured in the wind tunnel.

              6.1.3. Rolling resistance and drivetrain losses shall be measured using a flat belt or a chassis dynamometer, measuring the front and rear axles simultaneously.

              6.2. Approval of the facilities by the responsible authority

              The results of the wind tunnel method shall be compared to those obtained using the coastdown method to demonstrate qualification of the facilities and recorded.

              6.2.1. Three vehicles shall be selected by the responsible authority. The vehicles shall cover the range of vehicles (e.g. size, weight) planned to be measured with the facilities concerned.

              6.2.2. Two separate coastdown tests shall be performed with each of the three vehicles according to paragraph 4.3. of this annex, and the resulting road load coefficients, f0, f1 and f2, shall be determined according to that paragraph and corrected according to paragraph 4.5.5. of this annex. The coastdown test result of a test vehicle shall be the arithmetic average of the road load coefficients of its two separate coastdown tests. If more than two coastdown