## ISO Combination 1: truck + dolly + A-semi Cd = Ud + Wd; Smax = 1000kg
T =
Technically permissible maximum total mass (t) of the towing vehicle transmitted to the ground by the axles. (Permissible total weight of the truck in t)
Cd =
Mass (t) transmitted to the ground by the axles of the converter dolly including <strong>U<sub>d</sub></strong> (t). (Sum of the axle loads of the dolly t)
Rb =
Mass (t) transmitted to the ground by the axles of the semi-trailer loaded to its maximum total design mass. (Sum of the permissible maximum axle loads of the trailer in t)
Ud =
Mass (t) imposed vertically on the fifth wheel of the converter dolly. (Imposed load that affect on the fifth wheel dolly)
Wd =
Dolly tare mass (t).
L =
Theoretical dolly drawbar length (m), i.e. the distance between the center of the drawbar eye and the center of the axle assembly.
For a correct calculation only decimal places are separated with points.
Drawbar coupling:
D2 =
V2 =
Fifth wheel dolly:
D =
GCW:

1 Applicable to dollies with a rigid drawbar.
2 For dollies with a rigid drawbar, the Dc-rating shall exceed this calculated D-value.

## ISO Combination 2: tractor + A-semi + centre-axle trailer T =
Technically permissible maximum total mass (t) of the towing vehicle transmitted to the ground by the axles. (Permissible Total weight of the truck in t)
C =
Mass (t) transmitted to the ground by the axles of the center axel trailer.
Rb =
Mass (t) transmitted to the ground by the axles of the semi-trailer loaded to its maximum total design mass.
Ut =
Mass (t) imposed vertically on the fifth wheel of the tractor. (Imposed load that affects the truck in t)
L =
Theoretical drawbar length (m) of center axel trailer, i.e. the distance between the center of the drawbar eye and the center of the axle assembly.
X =
a =
Equivalent vertical acceleration in the coupling point, dependent on the kind of suspension on the rear axles of the towing vehicle including a constant factor. Air suspension and or equivalent a=1.8m/s2 and other suspension a=2,4m/s2.
For a correct calculation only decimal places are separated with points.
Drawbar coupling:
D3 =
V =
Fifth wheel dolly:
D =
GCW:

3 The Dc-rating of the drawbar coupling equipment shall exceed this calculated D-value.

## ISO Combination 3: tractor + A-semi + centre-axle trailer Cd = Ud + Wd; Smax = 1000kg
T =
Technically permissible maximum total mass (t) of the towing vehicle transmitted to the ground by the axles. (Permissible total weight of the truck in t)
Cd =
Mass (t) transmitted to the ground by the axles of the converter dolly including Ud. (Sum of the axle loads of the dolly t)
R1b =
Mass (t) transmitted to the ground by the axles of the first semi-trailer loaded to its maximum total design mass. (Sum of the permissible axle loads of the first semi-trailer in t.)
R2b =
Mass (t) transmitted to the ground by the axles of the second semi-semi loaded to its maximum total design mass. (Sum of the permissible axle loads of the second semi-trailer in t.)
Ud =
Mass (t) imposed vertically on the fifth wheel of the converter dolly. (Imposed load that affect on the fifth wheel dolly)
UT =
Mass (t) imposed vertically on the fifth wheel of the tractor. (Imposed load that affects the truck in t)
Wd =
dolly tare mass (t).
L =
Theoretical dolly drawbar length (m), i.e. the distance between the center of the drawbar eye and the center of the axle assembly.
For a correct calculation only decimal places are separated with points.
Drawbar coupling:
D2 =
V2 =
Fifth wheel dolly:
D =
GCW:

2 For dollies with a rigid drawbar, the Dc-rating shall exceed this calculated D-value.

## ISO Combination 4: truck + centre-axle trailer + centre-axle trailer T =
Technically permissible maximum total mass (t) of the towing vehicle transmitted to the ground by the axles. (Permissible total weight of the truck in t)
C1 =
Mass (t) transmitted to the ground by the axles of the CAT1. (Sum of the axle loads of the CAT1 in t)
C2 =
Mass (t) transmitted to the ground by the axles of the CAT2. (Sum of the axle loads of the CAT2 in t)
X1 =
L1 =
Theoretical drawbar length (m) of CAT1, i.e. the distance between the center of the drawbar eye and the center of the axle assembly.
t1 =
Distance (m) from the center of axles of CAT1 to its rear coupling point.
X2 =
L2 =
Theoretical drawbar length (m) of CAT2, i.e. the distance between the center of the drawbar eye and the center of the axle assembly.
a1 =
Equivalent vertical acceleration in the coupling point, dependent on the kind of suspension on the rear axles of the towing vehicle including a constant factor. Air suspension and or equivalent a=1.8m/s2 and other suspension a=2,4m/s2.
a2 =
Equivalent vertical acceleration in the coupling point, dependent on the kind of suspension on the rear axles of the towing vehicle including a constant factor. Air suspension and or equivalent a=1.8m/s2 and other suspension a=2,4m/s2.
For a correct calculation only decimal places are separated with points.
Drawbar coupling:
Dc3 =
V3 =
GCW:

3 The Dc-rating of the drawbar coupling equipment shall exceed this calculated D-value.

## ISO Combination 5: tractor + link trailer + A-semi (B-train) T =
Technically permissible maximum total mass (t) of the towing vehicle transmitted to the ground by the axles. (Permissible total weight of the truck in t)
R1b =
Mass (t) transmitted to the ground by the axles of the link-trailer loaded to its maximum total design mass. (Sum of the permissible axle loads of the first semi-trailer in t.)
R2b =
Mass (t) transmitted to the ground by the axles of the semi-trailer loaded to its maximum total design mass. (Sum of the permissible axle loads of the second semi-trailer in t.)
UT =
Mass (t) imposed vertically on the fifth wheel of the tractor. (Imposed load that affects the truck in t)
Ub =
Mass (t) imposed vertically on the fifth wheel of link-trailer.
For a correct calculation only decimal places are separated with points.
Fifth wheel B-train:
D =
GCW:

### Notice!

The ISO 18868 standard represents the current state of the art and is not a legal requirement. The user must specifically confirm his or her individual acceptance of the standard to the responsible state authorities.

This application can be used to determine the required minimum performance of coupling accessories (D and V value) for a specific vehicle combination in accordance with ISO 18868. JOST assumes no liability for the values calculated by the respective user.