Behind the wheel of a car that drives itself

It's more than a little unnerving when your steering wheel develops a mind of its own at 80 kmh.

After all, not being in proper control of your car is something that would earn you a sizeable fine - or a big repair bill.

But that's what I'm doing in what is one of the most advanced cars in the world. Mercedes-Benz has been referring to the technology available in the new E-class family car as the world's first self-driving car.

It's not quite, but it does take control in some situations, predominantly when it determines the car is not doing what the driver intended. Or, at least, what it thinks the driver intended.

The wheel writhes about under your fingers, so you feel slightly uneasy. It is difficult not to feel as though you should try to stop it from moving - it's a natural reaction -and many times I took back control of the steering.

The system will detect if you've taken your hands from the wheel via a torque (force) sensor, and if it detects the driver is being hands-off, it will emit a visual warning on the dashboard and an audible warning after 10 seconds, by which time it would usually be too late.

We tested the new self-driving technology in Spain under various conditions and it worked best in slow-moving traffic on a highway. The company claims the system will work at speeds between 0 and 200 kmh, though its cornering ability is lessened at higher speeds.

It's not perfect. In several situations it failed to do what was expected, steering the car slightly and then crossing the centre line. Luckily this was just a test.

What was clear after using the system for half an hour was that it's not a type of autopilot, as some may have expected.

Perhaps our expectations were too high, although Mercedes-Benz has been vocal about being first to market with the self-driving car.

Mercedes-Benz says the clever technology is not designed as an autopilot measure, rather as a safety system that can take some of the mundane elements of driving out of the equation. It can't take you to a set destination via the sat-nav system, and nor can it join cars in a queue.

But it can keep an eye on the road and do what the car in front does, which could be a good thing - or the exact opposite, depending on who you are following. The company says the system will help ''relieve motorists when driving is more of a burden than a pleasure - on the monotonous daily commute, for example''.

Peter Schmidt, who worked on the project, said the system is not about full autonomy, but is a step in that direction.

''It is only assistance. You have to have your hands on the steering wheel. The first step [it may be] for autonomous driving. But only the first step. I think there are several more steps in between before you have the opportunity for full autonomy.''

* Matt Campbell travelled to Spain as a guest of Mercedes-Benz.

-Fairfax News Australia