For decades, the idea of a car that could drive itself was the stuff of science fiction. As early as the 1930s US giant General Motors created a vision for a self-driving car. But in a world devoid of computers there was never any prospect of this becoming a reality; that early concept relied on smart roads for guidance – another non-existent technology at the time.

Fast forward eight decades and we still don’t have self-driving cars, or autonomous vehicles (AVs) as they’re now known. There’s plenty of talk about them though; the latest UK-based trials were announced only recently, but when will we be able to buy a self-driving car? Unfortunately nobody can say with any certainty, as there’s great debate over the likely timescales. Also, because they’ll cost lots to build, when they do arrive AVs will probably be available to lease only, rather than as an outright purchase.

All of the major car makers are working on autonomous tech because it’s assumed that in the near future it will become increasingly important in the marketplace. But there isn’t an obvious consumer demand for it. A recent JD Power survey found that just one in five of us would be interested in a self-driving car. It seems the auto industry and politicians are rather more excited at the prospect of AVs than consumers are. Perhaps that’s because many of us enjoy driving but it comes at a price.

According to the Association for Safe International Road Travel, more than 1.2 million people die in road crashes each year (nearly 3300 each day), with another 20-50 million injured or disabled. Self-driving cars could slash this toll because computers don’t suffer from fatigue, errors of judgment or road rage. But unfortunately, no computer yet built can compete with the human brain for processing inputs and making decisions.

Peter Shaw, of the UK-based Thatcham road safety research centre, reckons self-driving cars will cut crashes by 80%. But can autonomous vehicles ever become a reality? The simple answer is yes – but probably not as soon as we’re being led to believe. It wasn’t until recently that serious progress began to be made; huge advances in computerisation has allowed major advances in Artificial Intelligence (AI), which underpins the decision-making process that cars have to go through to drive themselves.

The thing is, for years car buyers have been making use of autonomous tech because that’s what driver assistance systems are. There are six levels to reach the truly autonomous car, with a truly self-driving vehicle sitting at level 5. These are the steps to a fully autonomous vehicle:

• Level 0: No automation at all.
• Level 1: Some driver assistance systems such as cruise control.
• Level 2:The car helps by steering, accelerating and decelerating but the driver is in control at all times.
• Level 3:The car is responsible for driving, but a human must be ready to take over if the sensors fail.
• Level 4:The car can drive itself within a specific zone.
• Level 5: The car can drive anywhere, in any weather.

When moving from one level to the next there’s always a huge gulf because total reliability is essential, which means the car has to be able to cope with anything from pedestrians and animals in the road to freak weather conditions. There are already cars on the market with level 2 autonomous tech and it’s hoped that next year we’ll see the first level 3 cars legally on European and US roads.

The point about legality shouldn’t be under-estimated, because while the technical hurdles to getting AVs on the road are immense, persuading our lawmakers that such technology is safe can be an uphill struggle. For example, Tesla has offered level 3 autonomous tech on its Model S since 2015, but the car was (and still is) too advanced for the legislation of the time.

After that level 4 is a big step, and with this allowing a car to drive only within a specific zone that’s fully mapped out, few consumers will be interested in such vehicles. What everybody is waiting for (but few people actually want, it would seem) is a level 5 car that can do the job of a human in any conditions. Many mainstream car makers are claiming that self-driving vehicles could be on our roads from as soon as 2020, but there’s no way that a level 5 car will be available so soon because there’s so much more development work to be done.

The first AVs will avoid crashes by using cameras, sensors and radar; where things become far more efficient and safer is when cars talk to each other and the street furniture. Currently, an autonomous car has to sense that a traffic light is red or green, but in the future the two will communicate with each other directly, to make things fail-safe – but this will require major (costly) infrastructure upgrades. In the future cars will also talk to each other, so they can learn from each other’s AI. So for example, if one car has to brake sharply for a hazard, any following vehicles will be warned so they can slow more gradually.

Car makers are now competing to be the first to bring a self-driving car to market which is why we hear bullish claims about the first models being available within the next three or four years. Many industry commentators claim that by 2030 most cars will either be highly automated or self-driving. Eberhard Zeeb develops driver assistance systems for Mercedes-Benz, and he isn’t so sure. He comments: “By the end of this decade we might have a level 3 car on sale but a level 5 car is unlikely to be available before 2030 at the earliest. But there are so many hurdles to overcome that fully autonomous cars that can be driven whatever the weather will probably not arrive until 2050”.

In most developed countries it takes 15 years for the car fleet to be renewed, so depending on who you believe, somewhere between 2045 and 2070 most cars will be autonomous. So if you’re upset at the prospect of self-driving cars taking over our roads, you’ve still got a bit of time to get out there and enjoy racking up a few more miles.

Richard Dredge