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GRAANGIDS
2016
GRAIN GUIDE
How is the permissible mass
of a vehicle determined?
Legislation with respect to the overloading of vehicles requires a basic understanding of the
reasons for overload control and the different aspects of the legislation regulating the loading of
vehicles. The loading instructions for a vehicle are very important, as Regulation 330C requires a
goods declaration in every goods vehicle to provide the consignor with the loading instructions of
the operator (owner).
The legislation in this regard is contained in Regulations 231 to 248 of the National Road
Traffic Regulations. The calculations below must be made for all vehicles to determine what
the maximum mass and the payload of the vehicle are.
Permissible maximum axle massload
Regulation 234 is a formula for determining the permissible maximum axle massload of a mo-
tor vehicle. Regulation 234 provides that the permissible maximum axle massload may not be
exceeded. That is the terminology used in the legislation. The three elements to be taken into
account for axles and axle units are:
• The mass that can be carried by the tyres
• The manufacturer specifications
• The limits (to protect the roads)
Regulation 238 provides that SANS 1550 must be used to determine the mass that the tyres can
carry. If the tyre is not listed, use the index on the side of the tyre.
Example:
An axle with two wheels on either side has a gross axle massload (GA) of 10 200 kg
and four size 11R22.5 tyres with a maximum tyre pressure of 850 and a maximum limit of
2 800 kg per tyre.
Calculation:
Tyres 2 800 x 4 = 11 200 kg
Specifications of the manufacturer, GA = 10 200 kg
Limit to protect the road, Regulation 240 (c) (v) = 9 000 kg
The lower of the masses above is the permissible maximum axle mass. Thus 9 000 kg / – depend-
ing on which is the lower mass – becomes the permissible mass. The same principle applies to
axle units. Prosecutions in terms of Regulation 235 are calculated on the same basis.
Regulations 236 and 237 – maximum permissible vehicle mass and combination mass
The permissible maximum vehicle combination mass or load is determined by Regulations 236
and 237. The calculation for a combination requires additional calculations. The elements to be
used to for determine the combination mass are:
• The sum of the axles. This means that the calculations done for the axles and axle units in terms
of Regulations 234 and 235 must be added together.