Eberhard Kaus waits until the nondescript, dark-coloured saloon has accelerated up to a speed of 100km/h before he simply takes his hands off the steering wheel.

Neither Kaus nor the car is fazed by the many intersections along the way, and his autonomous S-Class limousine gets on just fine in heavy town traffic where pedestrians are apt to stray suddenly across the road and speed limits are strict.

Throughout the journey, Kaus resists the temptation to intervene. His feet are off the pedals and his hands nestle in his lap.

Kaus is no ordinary test-driver.

He works for Mercedes-Benz and his test-bed vehicle plays a key role in the German company's strategy to come up with the perfect autonomous car.

Although the new S-Class just launched in New Zealand has a similar self-drive system, called Intelligent Drive, the driver's hand cannot leave the steering wheel for longer than 15 seconds before a warning is triggered.

Kaus has a vision that cars will soon be so smart that the driver is reduced to the role of being a passenger and computers assume control.

The vision prompted Daimler chief Dieter Zetsche to draw a parallel with the pioneering days of motoring. "We built the first horseless carriage 125 years ago and now we're getting close to making the first driverless carriage."

Carmakers are keen to sell vehicles with innovative driver-assist features which offer a degree of autonomy. But computer technology is not about to oust the driver completely.

Most drivers would still feel uncomfortable at the thought of the car making all the driving decisions - after all, the freedom and pleasure associated with motoring is important to many buyers.

Where eyes-closed, hands-free operation can play a major part is when driving turns to drudgery.

These include routine highway situations during commuting when cars edge forward bumper-to-bumper or monotonous long-distance trips when the driver could use his or her time more profitably.

This is the kind of scenario envisaged by Audi's development chief, Ulrich Hackenberg.

Kaus is more cautious. His prototype car halts obediently at red traffic lights, waits for pedestrians to traverse the zebra crossing and negotiates roundabouts with aplomb.

The technology behind all this is, however, still experimental and will not be seen in production cars for a few years to come.

Robot cars do well on special, demarcated routes if the driver is in a constant state of readiness and able to take avoiding action.

Mercedes development chief Ralf Herrtwich is optimistic about the future of driverless cars. The current S-class test car can already get through a typical traffic jam unaided, he says.

The next auto-pilot upgrade involves improving the sensitive video cameras and sensors on board with new software to make them more capable and responsive.

When that happens, driverless cars can finally shake off their science-fiction image. Researchers say it will probably take to the end of the decade to devise a motorway auto-pilot which could relieve the driver of responsibility at high speed.

Herrtwich believes the driverless concept could find its way into the next-but-one generation of Mercedes-Benz saloons.

Meanwhile Carlos Ghosn, who heads the Renault-Nissan alliance, has put company engineers under more pressure by promising to come up with an affordable driverless car from the marque by 2020.

To underscore his determination, Ghosn recently invited the media to watch him being chauffeured around a test track in an autonomous Nissan Leaf car.

Tesla boss Elon Musk is another fan of cars which can drive themselves. In various interviews he has announced that the company pipeline for the second half of the decade contains several electric cars.

These would delegate some 90 per cent of driving functions to a computer.

Most of the major manufacturers have staged similar demonstrations. BMW began dispatching prototypes with hands-off features on trips along the autobahn between Munich and Nuremberg several years ago.

Audi put driverless cars through their paces in various Las Vegas multi-storey car parks back in January, while component supplier Continental sent a car with pilotless features on a punishing tour of the US state of Nevada.

"We can now assess the sort of technical challenges facing us in coming years," says Herrtwich. By then a number of legal adjustments will need to have been made.

"The 1968 Vienna Convention on Road Traffic states clearly that the driver must be in control of his vehicle at all times," said the research chief.

German authorities are already working on appropriate solutions.

"By the time the technology has matured, some new laws will have to be in place, too," says the Mercedes-Benz development chief.