Last week one driver attacked another with an axe. Lewis Rushbrook looks at aggression on wheels
"I was all right until Kent Road," said a highly experienced motorist. "There I was, in the centre lane, minding my own business. But by the time 15 cars merged from the left and juggernauts charged through on the right, I was driving like a maniac."

What is it that turns normally responsible people into self-confessed maniacs, often leading to violence and damage? Struck by "road rage", drivers become so irritated that they act with anger or violence towards fellow road users.

In the claims department of Frizzell's insurance company, staff are convinced the phenomenon of road rage is increasing. Darren Wells, Frizzell's spokesman, says he and colleagues have accumulated around a dozen instances in recent months, a ratio unheard of previously. One woman was overtaken by a young male driving a BMW. She got so completely fed up by his swerving back and forth in front of her that when an opportunity arose, she came alongside and threw her lighter through the driver's window. Prosecuted for criminal damage, she received a fine, although the judge recognised mitigating circumstances.

More serious was a noonday assault in Kent. Motorist A overtook motorist B on the approach to a roundabout. The latter flashed his headlights in anger. Motorist A replied with a rude gesture, whereupon motorist B accelerated and overtook on the roundabout, skidding to a halt in front of motorist B, who couldn't avoid colliding. Motorist B leapt out, hauled the other driver through the open window of his car and beat him up on the roadway. Motorist A suffered a broken jaw, fractured collarbone and cracked right leg.

How widespread is road rage? Objective measures aren't easy to come by. Chief Inspector Phillips of the Metropolitan Police's HQ Traffic says that road rage is not a bookable (and therefore measurable) offence, though what results from road rage may be, such as "actual bodily harm" or "threatening behaviour". His colleague David Rowland is the Met Inspector who supplies footage from police video-cars for the infamous Police Stop videos and presents the second film in the series. He feels road rage may be increasing, as publicity uncovers more cases, but "usually it's just some arm waving and a few verbals. Where motorists go beyond that, it may be because society as a whole is becoming more violent, allowing an activity more common in the US to be copied here."

Others see a more obvious cause - congested roads. Increased congestion increases driver frustration, which in turn increases driver aggression. This is the view of Frank McKenna, professor of psychology at Reading University and an international authority on motorist psychology. He laments the lack of good statistics on road rage, but readily admits its reality. "The anecdotal evidence is there, and it's very frightening."

Reducing road rage is no easy matter, but Mr Wells maintains that a blueprint scenario appears time and again. If you are aware of the scenario, you are halfway there. There is always some kind of "incident" - whether being undercut, beeped at, overtaken - which triggers a response and leads to the insurance claims. So one way to fight road rage is through careful, caring driving, the educational aim behind the Police Stop videos. "Motorists need to keep thinking about their driving and about what other drivers are doing," says Inspector Rowland. "Roads are dangerous places and should be treated with respect."

Professor McKenna suggests three more strategies. First, don't "misattribute" the cause of an event. "When something happens on the road, it's automatic to assume the other driver did it deliberately to annoy you, and you respond accordingly, cursing or calling them names. Usually, it's nothing of the sort. The person has just made a mistake and it's nothing personal against you."

Second, even if you think it is deliberate, invoke the "just world" hypothesis - that one day this driver will get what he deserves - and get as far away as possible. McKenna thinks this is one of the few cases in which there is evidence for the "just world"; those who drive too fast or too close to those in front tend to be the ones who end up getting hurt. "Leave them to it and get out of their disaster zone."

Third, do nothing to raise the temperature of enraged drivers. If they charge out of their car towards you, stay put in yours. If there has been an accident, exchange information calmly. Dr Lea Brindle, an occupational psychologist and another expert on driver behaviour, agrees. "There's nothing worse than getting defensive. Swallow your pride. Use your counselling skills and listen, agreeing if you can, without admitting liability, but do all you can to de-escalate the situation."

Dr Brindle adds a fourth point. Stay in touch with your emotions. If you feel your own rage rising, try deep-breathing or counting to 10. Avoid fast, aggressive music, which tends to produce the same sort of driving. He suggests loosening your inhibitions, "scream to yourself in the safety of your car". Or you can always follow the advice on the A3 billboard: "Blow your horn before you blow your top."

Finally, all authorities agree that journeys begin with planning, not with turning on the ignition. Plan for congestion by building in contingencies or choosing less stressful routes. All these will increase the odds for rage-free motoring. In theory at least.