The hidden consequences of car dependency on population health

Australia’s growing reliance on larger, heavier vehicles is significantly exacerbating road trauma and accelerating climate change. Sports Utility Vehicles (SUVs) and utes now dominate new car sales, increasing the risk of death per kilometre travelled while emitting four times more CO₂ than smaller vehicles. Without urgent action, this trend will continue to endanger lives and push Australia further into a climate catastrophe.

Australian cities are deemed motor cities. More than 72% of Australians rely on vehicles for daily trips, whether it is dropping children at school, commuting to work, or shopping. This car dependency reflects the widespread residential-only development patterns now prevalent across all Australian cities. The health consequences are severe: significant health losses from physical inactivity, air pollution, and road deaths and injury, costing billions of dollars annually across all states and territories.

Globally, there is an urgency across many cities to move away from car-centric planning, advocating for 15-minute or 20-minute urban plans. These plans support greater levels of population and land-use densities to encourage a city of shorter distances in which residents can walk or cycle to local services. Expanding public transport, e-mobility, and road pricing are also being explored as ways to curb car dependency. Yet in Australia, car dependency continues unabated, with unprecedented growth in private motor vehicle numbers over the past decade.

Adding to the challenge of car dependency is the growing propensity for Australians to purchase larger and heavier vehicles. For example, in January 2025, SUVs and light commercial vehicles (mainly utes) made up to 83% of the new car sales in Australia. In 2024 alone, 700 000 SUVs were sold in Australia, accounting for 60% of total sales. The same trend has been reported in other car-dependent countries such as the United States (US), where nearly 80% of all motor vehicle sold in 2023 were trucks (light).

Australia’s car dependency is not only fuelling climate change, but the purchase of vehicles that are larger in size is leading to increased risk of death per kilometre travelled. Urgent action is needed to reverse this dangerous trajectory.

Bigger cars, bigger risks: the deadly and environmental toll

Recent US data reveal that vehicle size significantly affects road trauma. For every 10 000 crashes, the heaviest passenger vehicles result in 37 deaths, compared to 6 deaths for medium-weight vehicles and 3 deaths for the lightest vehicles. SUVs and large utes are particularly dangerous for pedestrians and cyclists. For example, an analysis of 700 000 fatal crashes found that replacing the growth in SUVs with standard passenger vehicles would have prevented 1 100 pedestrian deaths over a 20-year period.

Australian data tells a similar story: heavier passenger vehicles pose the biggest threat to life on our road. For instance, in Victoria, between 2012 and 2022, every additional 200 kg in vehicle weight led to 6.4 more deaths per 10 000 crashes (Figure 1). This pattern holds even when vehicle weights are restricted to 1000–4500 kg, which accounts for the majority of on-road traffic.

Not only are the larger and heavier vehicles more lethal in relation to road trauma, but the heavier vehicles also contribute, significantly, to global warming. The road transport sector is a significant source of greenhouse gas (GHG) emissions, particularly in Australia where private motor vehicle use makes up 92% of journeys. An analysis of 30 000 vehicles sold in Australia between 2012 and 2022, using data from Red Book, highlights that CO₂ emissions rise sharply with vehicle weight (see Figure 2). Smaller cars (under 1000 kg), emit as little as 90 g of CO₂-e per kilometre travelled, while heavier vehicles, such as four-wheel drives and SUVs exceeding 2500 kg, emit over 400 g of CO₂-e per kilometre travelled: more than four times higher. With the average Australian driving 11 900 kilometres per year, smaller cars total around 1 tonne of CO₂-e per year, whereas the heavy, four-wheel drives and SUVs emit approximately 5 tonnes of CO₂-e annually.

It is not sufficient to merely consider the tailpipe emissions across the motor vehicle fleets when estimating carbon emissions and hence, global warming. A full lifecycle assessment, factoring in manufacturing and disposal, reveals that large SUVs and four-wheel drives generate over 14 tonnes of CO₂-e over their lifetime, compared to just 4.9 tonnes of CO₂-e for smaller vehicles.

It is important to note that not only do heavier and larger private motor vehicles elevate the risks associated with road trauma and place increased pressure on the environment, but the heavier vehicles also contribute more to air pollution due to increased particulate matter emissions (PM_2.5 and PM₁₀), as their heavier mass requires greater braking friction, producing more harmful particles, worsening respiratory health risks.

Conclusion: the choice is ours

It is well known that Australia’s car dependency has resulted in an array of negative externalities including air pollution, physical inactivity, and road trauma. But what has been overlooked is the increasing propensity for heavier passenger vehicles on our roads and the resulting increase in road trauma and their significant contribution to global warming.

With over 80% of new vehicle sales being large, heavy cars, it is no coincidence that road trauma rates have not declined over the past decade despite numerous road safety strategies being implemented.

We can respond to this increasing lethality on the road transport network. There are opportunities for government to introduce policies that emphasise the safety rating of vehicles with respect to pedestrian, cyclist and electric micro-mobility road users linked to rebates and other incentives that discourage the ongoing growth in large and heavy vehicles being purchased predominantly for urban driving. Insurers could also play a role by incentivising premiums based on smaller-mid size vehicles.

Finally, as we know that our purchasing habits related to motor vehicles are exacerbating the crisis that is global warming, it is time that governments place a price on carbon: financial incentives are one of the key opportunities to influence behaviours and the continual growth in heavy large private motor vehicles in Australia not only kills and seriously injures too many Australians each year, but it is also leading Australia into catastrophic global warming and a hostile environment for future generations of Australians. We have a choice, and we need to act now.

Dr Mark Stevenson is Professor of Urban Transport and Public Health and Director of the Transport, Health and Urban Systems (THUS) Research Lab, The University of Melbourne.

Dr Jason Thompson is an ARC Future Fellow, Department of Psychiatry, The University of Melbourne.

Dr Omar Castrejon-Campos is a Research Fellow at the Transport, Health and Urban Systems (THUS) Research Lab, The University of Melbourne.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.  

The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated. 

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