Maximum Permissible Vehicle Mass

Transportation 2A

1. The below truck has a steering axle with 2 wheels and a 4 wheel axle at the back. The manufacturer’s specification for the maximum load carrying capacity is 17 000 kg. The tyre specification permits a carrying load of 2500kg per tyre.

The massload carrying capacity of the road as stated in the National Road Traffic Act of 1996, Regulation 240 state: No person shall operate on a public road a motor vehicle or a combination of motor vehicles, the wheels of which are fitted with pneumatic tyres, if –

(b) the axle massload of an axle fitted with two wheels and – (i) which is a steering axle, exceeds 7700kg.

11.1. Name the 3 limiting factors that influence the maximum permissible load that a motor vehicle can carry.

The maximum load on axle / axle units / maximum GVM specified by the manufacturer. √√

Load on tyres / tyre ratings √√

Massload carrying capacity of roads and/or bridges / Load on roads √√

(Alternative answer)

The maximum masses according to the carrying capacity of thetyresof the vehicle.

The maximum mass for which thevehicle itselfwas designed.

The maximum mass that theroad pavement(asphalt or concrete surface plus the underlying layers forming the structure of the road) can carry.

11.2. By using the information given answer the question. What is the maximum load that the National Road Traffic Act of 1996 allow this new truck to carry?

The Act specifies that all these regulations (limiting factors) are simultaneously applicable and that the one which prescribes the lowest mass for a particular vehicle is the one according to which it must be determined whether an offence has been committed.

Maximum load for truck = 17 000 kg √√

Maximum tyre load = 6 tyres x 2500 kg = 15000 kg √√

Maximum load on road = (7700 kg x 1 steering axle) + (9000 kg x 1 four wheel axles) √√ = 7700 + 9000 = 16700 kg. √√

Thus the limiting factor will be the minimum mass of the three which is the maximum tyre load = 15000 kg. √√