Experiencing regular incidents of road rage is highly dangerous to human health, research has confirmed.
Drivers consistently overestimate their own skills
Road rage - the irrational surge of anger towards another motorist - has many different causes, such as tailgating, cutting people off or the "theft" of a parking space.
It also varies in the response, which can range from a rude gesture or shouting to a full confrontation outside of the vehicle, sometimes with fatal consequences.
But Leon James, a Professor of Traffic Psychology at the University of Hawaii, US, told BBC World Service's Masterpiece programme that research had found the initial aggressive stimulation was very harmful to the body - especially if it recurred again and again.
"When you are angry, you are pouring stress hormones into your blood system, which are harmful to your heart and other functioning of the body," he said.
"So if we experience this kind of anger or impatience in driving every day, all our lives, you can see that over the years it's going to have a very strong negative health effect on the driver."
The problem stems from the fact that road rage places the driver of a vehicle in a "fight or flight" situation. Professor James described becoming angry behind the wheel as "driving under the influence".
Adrenaline is stimulated. The body's reaction prepares the muscles for a fight.
In some cases, motorists then get out of their cars and attack each other. This can even lead to a fight, as happens in the United States 1,200 times every year.
Drivers around the world are affected by road rage, and it may be worse in the developing world where roads and vehicles are in poor condition.
Professor James has been working with the Chinese government in an effort to reduce road rage amongst the country's truck drivers, eight million of whom are on the roads every day.
"Generally, if you look at the statistics, they are very sad," he said. "This year, over two million people around the world are going to die in traffic accidents. In 10 years, that's 20 million people.
"So it's a horrendous cost that we are putting up, and the point is that it is worldwide."
Studies have shown that drivers consistently overestimate their own driving skills, while believe other road users to be less adequate.
Closer to the edge
This coupled with the fact that cars lend a driver a feeling of being in a private, near-indestructible space makes road rage an ever-increasing phenomenon as more cars roll on to the roads.
Furthermore, recent US research showed that when people were asked to express their anger - for example by hitting a pillow - this just increased negative feelings.
This means that giving vent to feelings of road rage is only likely to worsen a driver's ability.
"Drivers who get angry on the road are certainly more dangerous," Steve Stradling, Professor of Transport Psychology at the Transport Research Institute, at Napier University, UK, told Masterpiece.
"When you're angry, you tend to lose concentration; you're likely to speed up and drive faster; you're more inclined to be rude and hostile to other drivers.
"All these factors will decrease a driver's safety margin, turning them into an accident waiting to happen."
'I shot him'
In the UK, the behaviour most likely to elicit physical aggression is when another driver nips in and pinches a parking space.
But the US Automobile Association website has stories of road rage that include "he was playing the radio too loud, so I shot him".
Car parks are the scene of much of British road rage
Interestingly, research has also found that there is little difference between men and women with regard to their emotional reaction to being treated badly in traffic.
"If we look at the whole age group, the differences become much smaller - in many studies, no difference at all," said Dr Timo Lajunen, a traffic psychologist.
"I think that one reason is that in the car, women can behave badly as well. So if you think about some aggressive incident or fight in a supermarket, naturally women wouldn't challenge a man in those cases.
"But in a car, it's the power of the car which matters, not the muscles."