Editorial: Danger from heavier loads simple physics

Photo / Paul Estcourt

According to the Ministry of Transport, trucks carrying heavier loads on our roads "will help to improve road safety, while reducing road congestion, operating costs and vehicle emissions".

The statement is a highly contrary one to critics of the move, who foresee only an increased threat to safety. They are apt to point out that trucks are involved in 16 per cent of all road fatalities despite comprising only 4 per cent of the vehicle fleet.

Allowing trucks to carry loads of up to 53 tonnes - an increase from the present limit of 44 tonnes - from next month can only, they say, make matters worse.

Basic physics supports their view. Heavier trucks will take longer to stop, thereby creating heightened danger for any motorist caught in their path.

But physics are not uppermost in the ministry's mind when it talks of safety. It hangs its hat on the productivity equation - that a given amount of freight will be carried on fewer trucks.

Safer roads, it says, will be the product of an estimated 20 per cent decrease in the number of trips by trucks, as will be an increase of productivity of between 10 and 20 per cent.

The latter benefit was emphasised by the Transport Minister, Steven Joyce, when he approved the change. He also noted that New Zealand's freight 'task' was forecast to rise by 70 to 75 per cent over the next 25 years.

Roads are expected to carry the bulk of that increase. That suggests any slowing in the increase in heavy-truck movements will be a temporary phenomenon.

If roads are so much more efficient as a mover of freight than rail or coastal shipping, there will surely be ever-increasing pressure for increases in the load limit. Otherwise, the number of trucks on the road will have to rise.

This, in turn, raises questions about the damage to the country's roads caused by heavier trucks. It needs to be noted that those carrying loads of 53 tonnes will be allowed only on specific routes, and will be subject to a new permit system.

Local authorities and the NZ Transport Agency will have the final say on whether roads and state highways, respectively, are suitable for heavier trucks.

This control over where trucks can go seems to have placated Local Government NZ. It says, similarly, that it has less concern over ratepayers having to pay bigger road-maintenance bills. Ratepayers will, with good reason, be somewhat less sanguine.

The ministry says the increased wear and tear on roads will be paid for through increased road-user charges. But local authorities will receive only 50 per cent of this as government subsidies, leaving ratepayers to meet the rest.

This is warranted, says the ministry, because ratepayers "benefit from the regional stimulus and economic and community benefits". Whatever the veracity of that, it does not justify the impost.

The biggest winner from the change will be trucking-company profitability. It would be more reasonable if, as the previous Government proposed, users of the permit system funded the additional road maintenance through extra operating costs.

Up to 5000 trucks will be eligible to carry heavier loads. The economic advantages are real enough. The Government has put an annual savings figure of $250 million to $500 million on the likely productivity gain.

Questions about safety and wear and tear on the roads are also relevant, however. Aside from the stringent checking of trucks, little can realistically be done about safety.

The Government may, however, have assuaged the critics somewhat had it ensured ratepayers were not seen to be subsidising trucking firms.

If heavier trucks are a necessary evil for economic growth, every effort should be made to ameliorate their impact on the public.