For several years now, more Australians have been dying on the road.

This trend is moving Australia further away from its Vision Zero ambition – a national commitment to eliminate all road deaths and serious injuries by 2050.

But what is driving the increase? And is the trend evenly distributed across different road users?

The answer to the first question is complex. The short answer to the second is no.

Historical data show for much of the past two decades, population-adjusted fatality rates for pedestrians and car occupants (drivers and passengers) broadly followed the same downward trajectory.

But since 2021, the two trends have started to noticeably diverge. Pedestrian fatality rates have been rising, while those for drivers and passengers have remained relatively stable.

Does this indicate some systemic change in our road system? We know vehicles on Australian roads are getting progressively bigger: more protective of their own occupants, but potentially more dangerous to those outside them.

Read more: Australia’s roads are full of giant cars, and everyone pays the price. What can be done?

Could that explain this divergence, at least in part?

To find out, we conducted the first Australian study to investigate this question using detailed pedestrian crash data.

We linked each crash to the size and weight of the vehicle involved and developed statistical models to isolate the contribution of vehicle size while accounting for other important factors.

The changing shape of Australia’s cars

Data show the average footprint (the ground area covered by the car) of light vehicles in Australia has increased by around 7% since........

© The Conversation