Radar to get Jaguar out of a jam

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Jaguar yesterday revealed an in-car device which could eliminate the frustrating motorway jams caused by volume of traffic.

The system, derived from military technology for guided missiles, consists of a radar linked to a cruise control. When activated, it takes over acceleration and braking from the driver to keep the car at a specified time gap from the vehicle in front. If another vehicle cuts in, the radar senses it and automatically slows the car until the gap is restored. Jaguar was yesterday demonstrating it "live" on the M4 in Wales.

"Simulations have shown that if just 40 per cent of vehicles were fitted with these, then it would cure motorway congestion caused by sheer weight of traffic," said Malcolm Williams, Jaguar's manager of advanced vehicle technology.

Many motorway jams are caused when drivers get too close in a lane, and then brake to increase their distance from the vehicle in front. On packed lanes this causes a "shockwave" to travel backwards through the traffic as successive cars brake unnecessarily, eventually causing what is known as "flow breakdown". The average speed falls, and the traffic may even stop completely. Drivers are then mystified by the apparent lack of cause for their delay.

Mercedes-Benz is understood to be preparing to introduce this radar system on some of its cars in 1997, and Jaguar intends to follow suit soon after. Mike Richardson, principal engineer in Jaguar's Advanced Engineering Group, said: "We would want to price it as an add-on, at about the same level as ABS braking, air conditioning or a good hi-fi."

The system, Autonomous Intelligent Cruise Control, provides the driver with a liquid crystal display in place of the rev counter. The cruising speed and time gap can be set separately, and then activated by pushing a button on the steering wheel.

If there are no vehicles in front, the car maintains cruising speed. As soon as another vehicle comes into the radar range - 135 metres, equivalent to four seconds travelling at 70mph - the radar locks on to it.

If the vehicle ahead is moving more slowly, the display flashes "Following", and brakes the Jaguar to match speeds and maintain a constant gap.

Jaguar is also developing systems for collision avoidance and night vision. But these will be more expensive and take longer to reach the domestic car. Mr Richardson also said that it would be extremely difficult to devise a system able to prevent incidents like Wednesday's coach crash that killed eight people. "It would need considerable investment in infrastructure: you would need roadside systems all linked to intelligent systems in the vehicles," he said.