Division 2.5.4.2

United Kingdom

For the road test the conditions shall be as follows:

Number of brake applications	20
Duration of a braking cycle	60 s
Initial speed at the beginning of braking	60 km/h
Braking applications	In these tests, the force applied to the control device shall be so adjusted as to attain the mean fully developed deceleration of 3 m/s² in respect to the towed vehicle mass P_R at the first brake application; this force shall remain constant throughout the succeeding brake applications.

The braking rate of a towed vehicle is calculated according to the formula given in point 2.2.3.5:

z_{R} = (z_{R + M} - R) \times \frac{(F_{M} + F_{R})}{F_{R}} + R

The speed at the end of braking:

v_{2} = v_{1} \times \sqrt{\frac{F_{M} + F_{1} + F_{2} ∕ 4}{F_{M} + F_{1} + F_{2}}}

Where:

z_R

braking rate of the towed vehicle,

z_{R + M}

braking rate of the vehicle combination (tractor and towed vehicle),

rolling resistance value = 0,01

F_M

total normal static reaction between the road surface and the wheels of tractor (N),

F_R

total normal static reaction between the road surface and the wheels of towed vehicle (N),

F₁

normal static reaction of the part of the mass of the towed vehicle borne by the unbraked axle(s) (N),

F₂

normal static reaction of the part of the mass of the towed vehicle borne by the braked axle(s) (N),

P_R

P_R = F_R/g

v₁

initial speed (km/h),

v₂

final speed (km/h).