It’s no secret that New Zealanders love using their cars to get from A to B – and many of our cities have been designed to cater to this.

In a 2017 OECD Environmental Performance report, New Zealand had the highest car ownership rates out of any OECD country, owning more vehicles per capita than the likes of Germany, the US and Japan.

It’s also widely acknowledged that reducing the number of cars hitting the roads has many advantages, including less air pollution, as well as the sheer time and money saved by having people stuck in bumper-to-bumper traffic.

But the health effects of reducing car-clogged roads in specific countries – or even towns – is less well researched.

Dr Caroline Shaw recently helped lead a study with the University of Otago to try quantifying this in New Zealand’s largest cities: Auckland, Wellington, Tauranga, Hamilton, Christchurch and Dunedin.

She says her team already knew from previous studies that a Wellingtonian’s transport habits will differ from that of a Jafa.

For example, just 0.5 percent of trips are taken by bike in Auckland, while 55 percent of households there have two or more vehicles.

In contrast, Wellington has the highest levels of walking and public transport use out of all the main cities, with 27.5 percent of the trips are done via walking and 6.2 percent done by public transport.

So, in order to break down and compare the health and carbon impacts and see how the major cities stack up against each other, Shaw’s team took an international model called the Integrated Transport and Health Impacts Model (ITHIM), a mathematical tool that measures the health implications of transport policies in different cities, and adapted it for New Zealand.

The data model measures four aspects of population health: total number of deaths, years of life lost, years of life lived with disability and disability-adjusted life years.

The results found that in every major New Zealand city, shifting away from dependency on cars reduced the number of people in all of these categories.

In other words: New Zealand moving away from its reliance on cars and towards other modes of transport, such as cycling or public transport, could result in significant health benefits, with a major reduction in premature deaths.

“When we put that in the model and saw the difference it made to health, it showed that if the other five cities had the same levels of walking and cycling [as Wellington], there’d be 200 less premature deaths each year, which is quite a reasonable number for the different cities,” Shaw says.

“There was also quite a reduction in carbon emissions – Auckland was 20 percent less and Hamilton was 22 percent less.”

It’s a noteworthy finding, especially considering New Zealanders have notoriously low levels of physical activity. An estimated 1435 deaths in Aotearoa in 2015 were attributed to people not getting enough exercise, while fewer than half of adults met national physical activity guidelines. If more people were getting out of their cars, Shaw’s finding indicate this number would drop.

The study also found that surprisingly, a shift away from cars results in overall injury and road traffic rates going down.

“That can seem counter-intuitive, because we know cycling is riskier than driving a car, for example,” Shaw says. “This model takes that into account that if there’s more people cycling, there’s a slightly higher number of people getting injured but even when you account for that, injury rates for car crashes go down because it’s getting people out of cars and into public transport, which is much safer for everyone.”

What’s more, balancing out the transport modes in our major cities would save a lot of carbon emissions. The study estimates that Auckland alone could save 430,000 tonnes of CO2 per year, a reduction of about 20 percent.

What’s all this mean? Shaw says the crux of the matter is reducing New Zealanders’ reliance on cars will improve both the nation’s health and the environment’s health.

She says two factors effect what mode of transport people choose: a city’s form, such as how dense it is and how easy it is to navigate around, as well as public transport accessibility.

These factors are affected by decisions that councils and central governments make, so she says there should be a conversation around values when looking at urban design.

“We need to think more broadly about transport – it’s not just about moving trucks across cities, it’s so much more than that. What do we value out of transport system? We need to value carbon and health outcomes, as well as moving people where they need to be. We need to look at what a transport system does to people’s health and their quality of life when living in a city, because we haven’t focused that.”

She says the new Government Policy Statement on land transport released this week is a great first step.

“They’re looking to put much more money into public transport, cycling and walking, so it’ll be interesting to see what it looks like in a few years’ time, but I think we need to have discussions about how we reduce carbon,” Shaw says.

“Transport is the fastest growing sector in carbon emissions – we’re not plateauing or even reducing – so it’s very difficult to see how we’d achieve our carbon goals without transforming the transport sector.”

One solution, as indicated by the study, is shifting away from cars as the main mode of transport in major cities.

Another move she says cities could take is using a model like the ITHIM model used for the study at local council levels to compare different modes of public transport and their carbon and health benefits.

Overall, she says it shows the power is in council and government’s hands to make a significant and positive difference to New Zealanders’ health.

“We can get injury benefits, as well as improving people’s mental health and physical activity. We know New Zealanders have low levels of physical activity, so any infrastructure we can put in place would be great for health.”