By EWAN KENNEDY
27 March 2006

Just who is driving that car on the road behind you? Is it the person sitting behind the steering wheel, or a little black box sitting somewhere under the bonnet

This thought came to me the other day as I was reading a press release from yet another upmarket car manufacturer boasting of the addition of distance control to its cruise control system.

In case you haven’t come across the term before, distance control holds the speed of your car to that of the vehicle in front. It does so by sending out a radar signal, processing the reply, then telling the cruise control to keep your car at a set distance from it.

Cleverly, it is less concerned with the distance as with the time to the other car. Generally it’s set to sit about two seconds behind the other vehicle, though you can vary this, perhaps to a single second or up to three seconds. The former being too close for comfort, the latter, sadly often encouraging impatient drivers to pull into that three second gap and temporarily destroy your car’s safety zone. Two seconds is just about right to my way of thinking.

The distance setting system generally only has to back off the throttle to maintain the preset time from the other vehicle, but can apply the brakes if need be.

As it works in conjunction with the cruise control, the distance control won’t exceed the speed you’ve set on the cruise. So there's no danger of your car suddenly setting off in wild pursuit of the guy in front who has just decided to blow the cobwebs out of his Ferrari Testarossa’s engine…

It all works well in theory and generally in practice. But as with so many automatic driving aids, automatic distance control can lull the driver into as sense of false security. For example, a businessman who feels secure in the knowledge that the radar is watching what's happening in front may feel it’s now a good time to check on those emails and text messages that have been beeping at him for the last couple of minutes.

Or Mum may feel it’s now OK to take her eyes off the road and reach back to adjust that blanket on baby.

Fortunately, there's a sort of wakeup feature in a distance control system. If another car slows suddenly, or a third party pulls into the gap in front of yours, the automatic application of the brakes certainly gets your attention.

My worry is that drivers making their phone calls and/or concentrating on replies to those important emails will soon get used to the brakes coming on by themselves and cease to be worried by it.

Regular readers will be well aware of my driver safety mantra: you should always have two hands on the wheel, two eyes on the road and 100 per cent of your brain on the vital job of driving.

This can certainly be achieved by whilst using a distance control system, but human nature being what it is, I’m not so sure it will always happen.