You have just overtaken a car on the M1. You look back in your mirror and see its driver staring daggers at you. Brace yourself, you are about to experience ...
When too many rats are thrown into too small a cage, experiments show, they attack each other. Given that 25 million vehicles clog Britain's roads, it is no surprise that road rage, an aggressive exchange between drivers, is reaching epidemic proportions.

Last year, one in six drivers was involved in a road rage incident, according to the annual Lex survey on motoring. Many were annoyed by drivers who cruised in the middle lane, overtook on the inside or were speeding in urban areas. While most drivers try to keep calm, others erupt at the first provocation. Two weeks ago, a driver in west London was attacked with ammonia in a road rage confrontation; in another recent incident, CS gas was sprayed in the face of a four-month-old baby. Some people are now afraid to drive on their own at night. A survey by the Norwich Union insurance company found that seven out of 10 women lock themselves inside their cars.

Dr Peter Marsh, author of Driving Passion: The Psychology of the Car, claims that road rage is not a new phenomenon. Indeed, the Oldie magazine recently published a story of "carriage rage" from 1817: "Last week I had a row on the road ... with a fellow in a carriage who was impudent to my horse. I gave him a swinging box on the ear, which sent him to the police, who dismissed his complaint," wrote Lord Byron to Thomas Moore.

Driving, says Dr Marsh, is an emotional activity. "The car is seen as an extension of the home. It evokes our territorial defences. If a cyclist touches your car or rests on the bonnet, it is seen as a violation of the body space. Cars are also a means by which we exercise control over a tumultuous world.

"Our lives are mostly dictated by other people," says Dr Marsh. "When drivers get into their cars they are in charge of what is happening. That sense of mastery can result in a sense of dominance. Anything seen as a threat to that dominance, such as a car coming close up behind, provokes an aggressive reaction. The car itself then becomes a kind of weapon. People who are usually mild-mannered start raising their fists. They are inside a protected environment. They feel safe."

Dr Marsh regards the design of headlights as particularly problematic. "Headlights give cars an animalistic quality - as do the four wheels. They are rather like horses. Lots of road rage incidents happen because people are not dipping their headlights. The headlights are seen as staring, threatening eyes."

Dr Roy Bailey, a clinical psychologist who specialises in corporate driving programmes, talks about cars as "dangerous, powerful animals". In the 20th century, he says, people have "techno-age brains and primitive bodies". Our minds may be sophisticated, but our nervous systems are not. It takes little provocation for many drivers to be pushed over the edge.

Dr Steve Stradling, a specialist in driver behaviour at Manchester University, disagrees. He believes that there are two types of people who are likely to succumb to road rage: "psychopaths" (people with anti-social personality disorders) or "narcissists" (people who believe that they are special, and that only they know what is right). "Both kinds of people are low on empathy," says Dr Stradling. "They find it hard to put themselves in the position of the other. They are also likely to misinterpret small incidents on the road and try to do something about it, either by punishing the person involved or by showing them how to do it 'properly'."

The best way to combat road rage, according to Dr Bailey, is to "release the anger and turn it into something else". Other, more practical solutions include stopping at service stations to have a massage (some masseurs offer soothing music, a leather head cushion and fragrant scents), taking a stroll, making a phone call, or even (as Richard Bremner, assistant editor of Car Magazine suggests), getting new car. "Some manufacturers are marketing their new cars as antidotes to road rage," he says. "The point being to tell the consumer that the car is calming and relaxing and enjoyable to drive."


Driven to violence

August 1995: Paul Gaynor, 26, is jailed for three months for head- butting a driver in East Finchley, London.

August 1995: Stuart Higginson, manager of a catering business in Ely, Cambridgeshire, is jailed for brandishing a toy gun at another driver.

August 1995: Paul Gaynor, 26, was jailed for 28 days for punching a bus driver in central London.

August 1995: a 25-year-old woman is punched in the face and clubbed over the head with a baseball bat on Grand Parade, Brighton.

September 1995: Sean Baldwin, 18, pleads guilty to punching and kicking a farmer on a country lane in Norfolk. The farmer was taking 48 cows home for milking.