The driverless car is here – yet it’s not for sale. The technology has been showcased by almost every major car maker in recent times.

In 2013 at the company’s AGM, Audi chief Rupert Stadler drove an A7 onto the stage via his iPhone, and BMW took journalists down autobahns in saloons that changed lanes by themselves, while Mercedes promises an autonomous S-class on sale in 2015.

The technology exists – in fact, even smaller makers such as Subaru have had the capability for decades – yet it’s not in showrooms despite GM sewing the seeds at its 1939 Futurama exhibit.

‘If you have flown in a modern airliner you have already experienced autonomous driving,’ says Volvo’s vice president of product planning, Toscan Bennett. Despite the promises, there won’t be a truly driverless car in your garage for some time yet. Here’s why.

Humans compute better

You know how to deal with lunatics, drunk drivers and bizarre scenarios, but the technology controlling driverless cars doesn’t. The road is such a complex, unpredictable environment that not every eventuality can be modelled. Human error causes 90% of accidents, yet we’re unrivalled at reading situations – our downfall is we’re often too slow to react. ‘The technology is the opposite,’ says Volvo’s senior vice president of R&D, Peter Mertens. ‘It has problems with recognising everything in a perfect way, but once [if] it has done so, it’s extremely fast.’ Take a falling tree branch as an example, and you get the idea. ‘You will never be able to – not in the next 10 years – completely model the world. Not even in 15 years I imagine.’

It’s still illegal

Ticking a box to make the autonomous car legal is not so easy. The single biggest hurdle is the 1968 Vienna Convention, which states that ‘every driver shall at all times be able to control his vehicle’. As well as convincing authorities that the driverless car is safe for public use through testing and demonstration, various governments have their own interpretations of what this means. The Germans see the autonomous car as contravening the Convention; the Swedes think that, because the Convention refers to the driver’s capability, not the car’s, it doesn’t prevent autonomous vehicles. Regardless, amending it is a massive challenge.

Who do we blame?

Where does ‘autonomous driving’ begin and ‘driver control’ end – and hence, who is responsible for collisions? ‘What about the first accident an autonomous car will have?’ says BMW’s Dr Werner Huber, head of automation. ‘Will the press quash all the visions, or will we have solutions to overcome that?’ This is a topic that will affect every car maker, so much so that several are working together on a legal framework to solve it. ‘The technology is already here – the challenge is legislation,’ says Volvo’s Toscan Bennett. ‘If there is a legal framework for it, the liability will fall into place.’

It’s already here

‘We already have some sort of autonomous control in the car at the moment,’ says Graeme Smith, chief engineer of UK engineering firm Ricardo’s Connected Vehicle, Control and Electronics group. ‘You put your foot on the pedal for ABS, as an example, and here’s a braking system that deactivates and reactivates the brakes. We’ve accepted this loss of control because we realise that in reality, it’s making the car safer’.

Add to that automatic parking systems, radar cruise control, electric steering, collision avoidance, emergency braking, even the automatic gearbox, and it becomes clear that we started handing parts of our driving over to computers years ago. ‘The ability to control the car is already there,’ says Smith.

We need a global system

A single global system must be implemented for cars to communicate with each other. Moving cars need to know what other cars are doing, as well as vehicles ‘off the grid’ – ie, parked. If not, mobility may be limited in the same way train-track gauges prohibited movement in the 19th century. How will an autonomous car recognise a stop sign or temporary diversion? They must all speak the same language. ‘If every manufacturer adopted a different system to operate, concepts like the road train [where autonomous cars slipstream each other, called ‘platooning’] would never work,’ says Smith. ‘There’s a lot of incentive for everyone to adopt the same operating system.’

Hacker fears

A case in the US – which sounds more like a crime fiction novel plot than reality – has seen a journalist killed after a car he was driving was allegedly hacked, with control taken over remotely. This suggested ‘cyber attack’ occurred on a regular vehicle, not an autonomous one, yet the increase of computer involvement has increased fears that cars that can be hacked into and stolen by remote control.

This must be overcome if the public and governments are to be convinced of the viability of autonomous cars. If they’re not failsafe, they’ll never be given the green light. It’s a relatively minor challenge, says Volvo’s Bennett: ‘Millions of people fly and travel on autonomous trains every day without giving it a second thought.’

You’re not ready for it

Volvo says its data shows that almost half of drivers aged 18-37 are open to buying a driverless car. Are we ready? ‘You bet,’ says Bennett enthusiastically. Yet that means that half of the population still needs convincing that autonomous cars are safe and offer a tangible benefit.

There is, of course, the enthusiast derision at the concept, too, but Gen-Y and beyond have shown a clear disinterest in cars, with smartphones and online connectivity seen as a higher priority. The autonomous vehicle can cater for that, as its occupants can communicate online instead of solely driving. ‘We believe that the majority of tomorrow’s car buyers won’t buy a car without this capability,’ says Bennett.

Semi-autonomous cars are better…

Mercedes, Volvo, BMW, Audi, Nissan: all have made it clear that the entirely driverless car won’t be here in 2015, perhaps not even 2020. The day when you have the faith to load your children into a car that drives them to school without you is a long way off. Yet the semi-autonomous car, which gives you the option for the car to take over in traffic, is both widely accepted and is essentially already on the road. ‘Who wouldn’t want to give up control of their car when stuck in traffic on the M25?’ says Nissan VP, Andy Palmer, a sentiment shared by BMW and Volvo colleagues.

‘I do think we’ll get to a point when we have fully autonomous, driverless cars,’ says Graeme Smith. ‘When will it happen? Who knows – maybe 2030 – but we will see manufacturers offering limited products before then,’ he adds. So, don’t take your hands off the steering wheel just yet, as you’ll still be driving for some time. No hope for the manual gearbox, though…