According to a study published in The Lancet Public health, road traffic injuries are expected to cost the global economy $1.8 trillion between 2015 and 2030, or 0.12% of global GDP each year. In 2018, the World Health Organization (WHO) estimated the number of deaths worldwide from road traffic accidents at 1,350,000 (compared to less than 1,200,000 in 2000). In more than half of the cases, the victims are the most vulnerable users: cyclists and pedestrians.
A key element of this problem remains the behavior of motorists. Road safety measures relating to vehicle safety equipment or the traffic law have multiplied in recent decades. With some success in Europe and East Asia, where mortality has fallen. But the trend is still upward elsewhere.
In road safety policies, the link between risky driving behavior and car size has hardly been factored into the equation. But it is by understanding what makes drivers take risks that we can also reduce road accidents and limit their impact on society.
This relationship between car size and risk taking is not obvious. On the one hand, consumers feel safe when they choose large cars. On the other hand, statistics suggest that large cars are far more often involved in accidents, which could indicate that drivers of large cars take more risks.
There are more and more large cars on the roads. According to the International Energy Agency, there were at least 35 million more SUVs on the roads around the world in 2021, with record levels in France, the UK, Germany and China.
At the same time, the best-selling models have grown in volume for a few decades. A study by UK specialist credit broker Zuto provides some interesting examples: the size of the Ford Mustang has increased by 63% since 1964, and the Mini by 61%.
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If the size of vehicles affects the behavior of motorists, this race for volume will have negative consequences for traffic accidents. This observation led us to explore the following idea in our research: do large cars give drivers the impression of having a “safety cushion” that would encourage them to take more risks?
We used an extremely realistic driver training simulator to test the driving differences between small and large cars. The simulator settings remained the same, but participants were told that they were driving either a small car (Toyota Yaris) or a large car (Toyota Avensis Wagon). They were asked to drive normally during the simulation.
The results showed that participants who thought they were driving a large car drove more sportily and engaged in more risky behavior than with a smaller car. However, the car was the same, with an identical response when pressing the accelerator or the brake. Only the behavior changed. They therefore believed that they were better protected in the big cars and took more risks.
Higher overall risk taking
Another experiment showed that this higher overall willingness to take risks has other consequences. We asked ourselves if drivers also took more risks when they got out of their vehicle, and we noticed that the feeling of security provided by the car was actually a good indicator of overall risk taking, that is, even without for the road.
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Other studies support this finding. For example, previous research has shown that truck drivers often have an accident shortly after leaving their vehicle. The explanation is that the feeling of security inside the truck extends outside the vehicle and leads to excessive risk taking.
The risk-taking therefore takes place on different levels, at the wheel of the big car and then once outside the cockpit. The “safety cushion” effect can also encourage a person to buy or refrain from buying a lottery ticket at a gas station or a drink instead of someone else.
A new malus in France
These findings therefore encourage governments to prioritize taxation based on vehicle weight or size, which already exists in many European countries, for road safety purposes. In France, a law imposing a fine of 1800 kg has been in force since 2022.
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These measures would be all the more justified as large cars can also cause greater damage in the event of an accident due to their size and put more strain on the infrastructure: they damage the roads more and need more space for parking.
Knowing this, infrastructure can also be designed to save lives. If the streets are narrower, the risk to drivers of large vehicles will be less because they will slow down.