If it ain't bust, why fix it, goes an adage with the ring of reason to it.

So the first step in considering government proposals to reform this country's vehicle licensing regime is to assess whether the system is faulty.

A key point is that the current regulations require six-monthly testing of all vehicles from the time they are six years old - and this is said to be the most regular safety inspection requirement in the world. Some comparable countries expect annual inspections, others once every two years.

Others, such as most parts of Australia and the United States, require no regular inspections at all.

However, despite the warrant-of-fitness testing regime, the number of crashes caused by vehicle faults in New Zealand is roughly the same as in other countries. According to the Automobile Association, less than half a per cent of crashes in this country have as their sole cause the sort of vehicle faults identified in WOF checks. Where such faults are contributing factors, the rate is still a minimal 2.5 per cent.

According to the AA, New Zealand motorists are burdened with the higher cost of regular inspections for no obvious gain in terms of safety. Another statistic it points to in backing a more liberal testing regime is that 40 per cent of the vehicles involved in fatal crashes didn't have a current WOF.

The fear is that, as with many compliance issues, a wide net is capturing the "good" majority while being swerved around altogether by a rogue minority. There will be wide support if the aim and outcome of any reform targets categories of vehicle most likely to be causing the greatest risk, while reducing the costs and demands of the rest of us.

One worry in liberalising the testing regime is whether it hands even greater responsibility for safety standards to the police. While they must deal all too often with the results of unsafe driving and vehicles, they are not necessarily mechanical experts, roadside checks are much less thorough than those conducted in garages, and surely officers have better things to do. According to the Motor Trade Association, about 275,000 vehicles are being driven around without warrants, while last year only 36 per cent of vehicles received their warrants by the due date. The people who most flagrantly breach the law now will be even less likely to ensure their vehicles are safe if the regulations are relaxed.

Successive governments have been campaigning for years to get the road toll down. Any WOF reform that could be seen as compromising safety carries clear political risks. Kiwi ingenuity is all very well, but cars held together by fencing wire with illegal modifications, painted-over rust and standing on bald tyres put more than their own users at risk.

New Zealand roads are challenging compared with some more highly populated countries and the national fleet has a long tail, with too many vehicles kept in service well past their use-by date. However, it's not only the old dungers that fail in the six-monthly WOF inspections. How many otherwise law-abiding motorists would check and where necessary replace or adjust their tyres, brakes and headlights regularly unless they had to? Reform would likely be welcomed by many drivers, but the Government must drive change with caution.

- © Fairfax NZ News