Division 5.1.1.1 The road load force for an individual vehicle shall be calculated using the following equation:F1

is the calculated road load force as a function of vehicle velocity, N;

is the constant road load coefficient, N, defined by the equation:

$f_0=\mathrm{Max}\left(\left(\mathrm{0,05}\times f_{\mathrm{0r}}+\mathrm{0,95}\times \left(f_{\mathrm{0r}}\times \mathrm{TM}∕{\mathrm{TM}}_r+\left(\frac{\mathrm{RR}-{\mathrm{RR}}_r}{1000}\right)\times \mathrm{9,81}\times \mathrm{TM}\right)\right);\left(\mathrm{0,2}\times f_{\mathrm{0r}}+\mathrm{0,8}\times \left(f_{\mathrm{0r}}\times \mathrm{TM}∕{\mathrm{TM}}_r+\left(\frac{\mathrm{RR}-{\mathrm{RR}}_r}{1000}\right)\times \mathrm{9,81}\times \mathrm{TM}\right)\right)\right)$

is the constant road load coefficient of the representative vehicle of the road load matrix family, N;

is the first order road load coefficient, N/(km/h), and shall be set to zero;

is the second order road load coefficient, N/(km/h)², defined by the equation:

$f_2=\mathrm{Max}\left(\left(\mathrm{0,05}\times f_{\mathrm{2r}}+\mathrm{0,95}\times f_{\mathrm{2r}}\times A_f∕A_{\mathrm{fr}}\right);\left(\mathrm{0,2}\times f_{\mathrm{2r}}+\mathrm{0,8}\times f_{\mathrm{2r}}\times A_f∕A_{\mathrm{fr}}\right)\right)$

is the second order road load coefficient of the representative vehicle of the road load matrix family, N/(km/h)²;

is the vehicle speed, km/h;

is the actual test mass of the individual vehicle of the road load matrix family, kg;

is the test mass of the representative vehicle of the road load matrix family, kg;

is the frontal area of the individual vehicle of the road load matrix family, m²,

is the frontal area of the representative vehicle of the road load matrix family, m²;

is the tyre rolling resistance of the individual vehicle of the road load matrix family, kg/tonne;

is the tyre rolling resistance of the representative vehicle of the road load matrix family, kg/tonne.