Road trains are becoming a more common feature in the South African Mining landscape for the efficient transport of both raw and beneficiated minerals over distances between 5 and 100km. A road train is typically defined as a prime mover or truck tractor that typically pulls anything between two and six trailers behind it, and the total weight of these train combinations varies between 100 and 400 metric tons.

In typical mining applications these prime movers most often pull side-tipping trailers when large bulky material is transported, and bottom dump trailers are most often employed when free flowing easy discharge materials are transported.

Currently there are four locations in South Africa where Road trains are used very successfully in the transport of large quantities of minerals, the largest single operation of this type being Richards Bay Minerals where in excess of 300 000 tons a month of raw material is transported by road train over a lead distance averaging around 20km.

The so called Road train originates back to just after World War 2 when the Australian government with the help of the Americans during World War 2 had established a rudimentary surfaced road network to supply Australia’s north coast with troops and munitions to counter the threat of invasion from Japan. Because there was very limited access to Australia’s Northern Territory, (an uninterrupted rail link from Alice Springs to Darwin was actually only completed within the last ten years) road transport was the most popular mode of transport. The vast huge distances and flat country brought the realization that it would be practical to couple a number of trailers behind a single prime mover and this would provide a huge improvement in the efficiency of the transport operation together with significant reductions in cost.

Considering that mining and natural resource industries both in Australia and Southern Africa are often located in geographically remote areas, and the relatively low value of unprocessed minerals, it is a natural progression that road trains should be employed for the transport of large volumes of raw product.

Traditionally mining operations have used either conveyor belts or private railways for the transport of raw materials over extended distances. Both of these transport modes are both very capital intensive over long distances, requiring long payback periods, and highly inflexible. A road train on the other hand is both highly flexible and versatile and can easily be deployed on different routes very easily with low capital cost by comparison.

The most popular Road train execution is probably the so called A triple which would comprise a 6x4 truck tractor (three axles or six wheels and two of the axles or four wheels are driven) with a three axle semi trailer followed by a two axle dolly coupled to another three axle trailer followed by another two axle dolly and three axle trailer. Each of the trailers would carry a payload of around 35 metric tones offering a total payload of between 105 and 110 tons, and the total rig would weigh in at a total mass of around 150 metric tons. This combination can safely travel and stop from a cruise speed of 80km/h.

Although large axles and tyres can be employed, similar to those on the well known coal haulers which is a converted rigid off highway truck with trailer, most road train equipment runs on axles and tyres where the axle load seldom exceeds 9000kg. The reason for this is that the haul road required does not have to be built to a spec any higher than our national roads, and in certain circumstances in remote areas the government has granted permits to run vehicles like this on roads which the public also use.

In order for a Road train to be given permission to travel on South African roads that the general public also has access to the vehicle has to comply with the road traffic act in all respects including braking, lighting, dimensions, axle weights and homologation by the SABS. Exemption is given in terms of overall length of the combination, which is around 45m versus the normal legal max length of 22m, and the gross combination weight of the combination is around 150 000kg versus the normal legal maximum of 56 000kg.

In terms of operating economics, a Road train when compared to a classic interlink combination that runs three standard 6meter containers on the Durban Johannesburg route, an A triple road train moves roughly three times the payload (105t versus 35t), using double the fuel of the interlink. The Road train requires a capital investment of roughly 2.5 times a typical interlink (side tip interlink versus side tip road train), has a maintenance cost of roughly double that of an interlink, and only needs one third of the drivers that interlinks require to move the same tonnage. In broad economic terms it can be seen that the cost of a road train is typically around two thirds that of the biggest street legal truck in terms of rand per ton moved.

Western Star trucks, a brand of Daimler Chrysler and represented in South Africa by Liebherr Africa is one of the foremost suppliers of road train type prime movers in the world, and specializes in custom building truck tractors that are employed in road train applications. In addition to this Western Star also builds a range of rigid 6x4 off-highway dump trucks which have proved themselves over the last four years in South Africa to be a highly cost effective option in hauling material at high speeds over previously uneconomic lead distances from pit to hopper.

Because of Western Stars custom built approach to building trucks specifically for application, the 30 and 40 ton class dump trucks offered in South Africa have proved to be ideally suited to South African conditions where hauls are often longer than typically contemplated in mining operations elsewhere in the world. These highly productive trucks complement the proven productivity of Liebherr excavators and wheel loaders also sold and supported by Liebherr Africa. Liebherr Africa can be contacted on 011 365 2000. The specs for Western Star trucks are available on http://www.westernstartrucks.co.za.