NZ’s old cars a public health hazard

NZ's car fleet is one of the oldest in the developed world, writes the University of Auckland's Kim Dirks. So what does that mean for pollution levels? 

It has been reported that the national fleet of cars in New Zealand has an average age of 14.2 years, nearly twice that of the UK where the average is 7.7 years, making New Zealand’s vehicle fleet one of the oldest in the developed world. Indeed, it has been stated that within our fleet, one in five vehicles is over 20 years old.

These older vehicles produce much higher levels of emissions than newer vehicles so what does this mean for the levels of pollution in the air?  And what does it mean for people’s exposure, and ultimately their health, and what can we do about it?

These questions, and specifically the effect that the vehicle fleet has on the air pollution exposure of people walking along busy roads at peak hour traffic, is being researched by a team at the University of Auckland.

We know already that these very old vehicles contribute disproportionately to the problem of emissions and we have been able to prove that by using portable air pollution monitors which show spikes in air pollution levels that coincide with certain cars.

This means we can identify which specific vehicles are the culprits. But it’s not enough to identify the worst polluters – we need to know what this means for people’s exposure to air pollution.

There is an old saying that "If a tree falls in a forest and no one is around to hear it, does it make a sound?” Air pollution exposure works much the say way.

If there are no people about where the vehicles are emitting, then they will have much less impact on the population than if emitted where there is a high density of people. This is even more the case if the people are a high-risk subset of the population, such as children or the elderly.

With this in mind, the most effective strategies for reducing the impact of vehicles on the population must either target the very old vehicles specifically and/or change where and when the emissions occur in relation to people and, specifically, vulnerable groups.

With regard to targeting these older cars, suggestions have been made to change the regulations surrounding the importation of used vehicles. Stricter rules would result in an improvement in emissions, especially as many of the imported used vehicles are currently high-emitting SUVs.  

A note of caution though – it is important to ensure that these restrictions do not result in a stronger demand for older vehicles due to an increase in their scarcity which would bump up the price and make them more sought after. As suggested by Associate Minister for Transport Julie Anne Genter: “We don’t want to create perverse incentives like people holding on to older cars for longer”.

Simply scrapping older cars is another option but there are equity issues that arise – those who own them are often the least able to afford an upgrade.

One option is to look at incentivising the top of the fleet which would have knock-on effects all the way down the fleet due to the availability of cars as people upgrade. We have seen this, to some extent, with the introduction of incentives such as priority lanes for electric cars.

This would have encouraged some owners of relatively new petrol/diesel cars to ‘upgrade’.  Their relatively new car would then be on the market for those looking at upgrading from the next tier down…and so on, down the supply chain to the oldest cars.

With regard to strategies around the impact these vehicles have on health – the greatest adverse impact occurs when a high density of people intersects with a high density of vehicles – for example, the morning rush hour.  

Some of our worst polluters are school buses. These buses congregate, by their very purpose, around schools, where there is a high density of children, at the time of days when air pollution levels are at their worst. Yet, bus companies tend to use some of their oldest vehicles for the ‘school runs’.  

Inner city routes tend to be prioritised for the use of low emission and electric buses, the argument being that these routes can be expected to offer the greatest benefit due to the high density of people who would otherwise be affected by the air pollution produced. But school runs should also be prioritised as children congregate on the streets leading to school and around the school exactly at the time when the buses are there.

Finding a way to incentivise bus companies to use low emission (or electric) buses on school runs would be a highly effective way of minimising the impact around schools.

Protecting our children from their very direct contact with some of the very worst traffic polluters seems a logical place to start on the issue against toxic older vehicles – and more, it would be a cost-effective strategy for minimising the adverse health impacts of air pollution exposure to the population as a whole.

Newsroom is powered by the generosity of readers like you, who support our mission to produce fearless, independent and provocative journalism.


Newsroom does not allow comments directly on this website. We invite all readers who wish to discuss a story or leave a comment to visit us on Twitter or Facebook. We also welcome your news tips and feedback via email: contact@newsroom.co.nz. Thank you.