You may have noticed - there's a car-size inflation on Australian roads that some have nicknamed car " mobesity ".
Author
- Milad Haghani
Associate Professor and Principal Fellow in Urban Risk and Resilience, The University of Melbourne
Most SUVs and utes from a decade or two ago look small next to today's models .
As we head for a fifth consecutive year of rising road deaths and what could be the worst year for pedestrian fatalities in nearly two decades , it's time to look more closely at what this means.
We already know bigger cars cause greater impacts in collisions .
But what's less discussed is whether driving one also changes how we drive - if larger vehicles make us feel safer inside them, do they also make us take more risks behind the wheel?
What's driving this trend?
Four in five new cars sold in Australia are SUVs or utes - more than double the share of 20 years ago .
This isn't purely consumer-driven.
With no domestic car manufacturing, Australia imports vehicles shaped by global production trends, many of which trickle down from United States policies that reward larger vehicles.
Two subtle US policy features explain why.
First, the " SUV loophole ": under US law, most SUVs are classified as light trucks, meaning they're subject to less stringent fuel-efficiency and crash-safety standards than passenger cars.
Second, under US fuel economy rules , fuel-efficiency targets are adjusted based on the size of the vehicle's "footprint" - the area between its wheels. In practice, this means larger vehicles are allowed to consume more fuel while still meeting the target.
Together, these rules have encouraged American manufacturers to build and sell heavier SUVs and utes.
Large vehicles can deliver significantly higher profit margins than small cars.
These trends have resulted in more bigger cars being driven on Australian roads.
The combination of high car ownership, years without fuel efficiency rules , and the luxury-car-tax exemption that many utes qualify for has made Australia a highly lucrative market for large, high-emission models.
Marketing has played a significant role too: in 2023, car makers invested about A$125 million in SUV and 4×4 advertising in Australia - a 29% increase from the previous year.
The dangers of bigger vehicles
There's a physical mismatch between large and small vehicles that usually transfers the danger from the occupants of the bigger car to everyone else.
While the risks of being hit by a large SUV or ute might seem self-evident, the question is how much greater those risks are.
Research provides a clear answer.
Car-to-car collisions:
Collisions between large SUVs and smaller cars show occupants of a smaller vehicle face about 30% higher risk of dying or sustaining serious injury.
A 500kg increase in vehicle weight is linked to a 70% higher fatality risk for occupants of the lighter car.
For every fatal accident avoided inside a large vehicle, there are around 4.3 additional deaths among other road users.
Car-to-pedestrian and cyclist collisions:
Pedestrians struck by SUVs are about 25% more likely to sustain serious injuries and 40-45% more likely to die than those hit by smaller cars.
For children, the outcomes are far worse: they are up to eight times more likely to die when hit by an SUV than by a small car.
Each 10cm increase in front-end height raises the fatality risk for pedestrians by roughly 20% .
Tall and blunt fronts ( vertical or nearly upright front design ) are associated with more than a 40% increase in pedestrian death when compared with low and sloped front ends.
These differences help explain why US pedestrian deaths - once on a steady decline - have climbed back to their highest level since the early 1980s.
This is while most countries have reduced pedestrian fatalities .
Bigger cars, more risk-taking?
Evidence from multiple countries suggests driving larger vehicles may lead to more confident or risk-prone behaviour :
India: SUV owners recorded 20-25% higher risk-taking scores than sedan or hatchback drivers
Israel: an analysis of 1.5 million speeding citations found drivers received about a quarter more speeding tickets when vehicle mass was 10% heavier
Austria: roadside observations of 48,000 vehicles showed SUV drivers more frequently drove without seatbelts, used phones and ran red lights. Women SUV drivers showed violation rates similar to men, breaking the usual pattern of higher female caution in traffic studies
New Zealand: field data found SUV drivers 1.5 times more likely to drive one-handed, a behaviour linked to lower perceived risk and reduced vigilance
Germany: large-car drivers reported higher rates of traffic violations and risky driving .
Policy can make a difference
Taxes and size-dependant registration fees could potentially offset some of the extra costs of heavier vehicles on roads surfaces, congestion and emissions , or regulate demand.
Two measures would make a tangible difference:
Licence testing by vehicle class
Many drivers obtain their licence in a small sedan but can legally drive a two-tonne ute the next day. Yet, larger vehicles demand different manoeuvring skills, longer braking distances and greater spatial awareness .
Requiring a practical test in a vehicle of comparable size to what the driver intends to drive (or a streamlined license upgrade for an experienced driver when upsizing) would acknowledge that added responsibility.
The reform would also carry a symbolic message: driving a heavier vehicle comes with greater responsibility.
Penalties scaled to impact potential
A ute or SUV travelling 10kmh over the limit carries greater kinetic energy and longer stopping distance than a small sedan.
A tiered approach - where fines or demerit points scale with vehicle mass - would better reflect the disproportionate risk that bigger cars pose.
If Australia is serious about reducing road trauma, these are the kinds of targeted, evidence-based adjustments that should be considered.
Milad Haghani receives funding from The Australian Government (The Office of Road Safety).
