ONE of the most dangerous moves a driver can make on the highway is to tailgate the car in front of him. When a driver has his nose almost touching the rear end of the vehicle in front, he is said to be tailgating.

This leaves the driver following with no reaction time and certainly no braking distance. The result can be disastrous. See the accompanying photograph.

Tailgating is best left to Mika Hakkinen as he follows Michael Schumacher on a Formula One circuit. Here's how it works. When a car, bus, truck or train goes by at high speed it creates a vacuum in its wake. The air surrounding the rear end of the car rushes in to fill the vacuum which is why your clothes flap and bits and pieces of debris like plastic bags on the road start to fly and follow the car. The vacuum thus created can hold the car back, slowing it down. And it also increases fuel consumption.

The rear end of a car is well rounded to allow a smooth flow of air, not allowing a vacuum to be created.

These days it is normal to see spoilers on the rear deck of fast cars like the Lancer, Honda and Astra. This is to avoid air turbulence by allowing the air to flow smoothly.

Schumacher's F.1 Ferrari moves at speeds of over 250 kmph. A vacuum is created under the car and as air rushes in to fill the vacuum it could lift the rear tyres off the tarmac. To counter this, the Ferrari has a huge aeroplane-type wing on the rear of the car. It produces a downward

thrust to keep the car glued to the road. It also deflects the air upwards. Were it to be allowed to remain at the ground level, the turbulence would destabilise Mika's car which is almost touching Michael's car.

Why does Hakkinen make this extremely dangerous move? Firstly, its safe for him because Michael is going to go faster and is not likely to slam his brakes. Secondly, it allows the car to fill the vacuum. This forward suction gives him extra speed. It also improves fuel consumption. This could mean one pit stop less to refuel. All it takes is 5-6 seconds. That is enough to allow David Coulthard, lying third, to zoom into second place. A position lost!

Tailgating is fine for Formula One drivers but not for driver on the highway.

It is the responsibility of the driver attempting to overtake to maintain a safe distance. Also an overtake should be attempted when the road and vision is clear.

The driver of the Sumo in the photograph slammed his brakes when a cow jumped off the central road divider. The Maruti 800 which was following the Sumo was in an extremely dangerous situation: Too close, no braking distance, no reaction time. The driver's vision had been completely obstructed by the huge rear end of the Sumo. Had he maintained a safe distance, he may have been able to see the cow jump off the road divider.

Tailgating is extremely dangerous. And extreme danger is the only ingredient required for disaster.

Add to all this the fact that the Sumo has a very soft suspension. In extreme braking situations, like the panic stop that the Sumo made, the nose dives horribly, lifting the tail end. Enough to allow the low gently sloping bonnet of the 800 to slither under the Sumo, right up to the windscreen. When both vehicles came to a dead halt (no pun intended), the Sumo levelled off, sat back on its rear suspension, and further crushed the 800.

Moral of this story — maintain a safe distance.

Happy motoring.