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An investigation into the feasibility of increasing the legal loads for heavy vehicles on New Zealand roads was begun in 1993. Roads carrying major flows of heavy vehicles in both the North and South Islands were identified, and those that have potential to be used as heavy transport routes were selected. These are routes that carry significant flows of heavy vehicles, and that have a clear purpose (eg mill to port).

To evaluate the potential for increasing the legal gross weight of heavy vehicles that could be carried on these heavy tranport routes, the route between the wood-pulp mill at Kinleith, near Tokoroa in the centre of the North Island, and the Port of Tauranga on the Bay of Plenty, was taken as a pilot.

The main concern was to evaluate the road geometry and vehicle weight constraints of the pavements and bridges along the pilot route. To determine the maximum axle weights and gross vehicle weights that the bridges on the route could safely accommodate, a methodology based on the use of the Transit New Zealand overweight permit system was developed.

For the eight heavy vehicle types tested, a significant increase in gross vehicle weights can be used on the pilot route. For the current legal vehicle types these gross weight increases range from 12% to 25% of the current legal weight limits.

Keywords: Freight transport, heavy transport, heavy vehicles, New Zealand, roads, routes, transport, vehicles