Tesla Model S Autopilot
George Hotz believes he can take on Tesla and its self-driving Autopilot featureReuters

A decade after he became the first person to crack the iPhone, George Hotz is back and this time he is jailbreaking cars. The 27-year-old has released free code and instructions to 3D print a device he says can make certain cars autonomous.

Through his start-up company called Comma.ai, Hotz had originally hoped to sell the plug-and-play device for $1,000 (£800), plus $24 per month, on Amazon, but the US National Highway Traffic Safety Administration stepped in, cited safety concerns and convinced the hacker to change his mind.

Now, the code is available to download for free, along with instructions on how to 3D print the small device which fixes to a car's windscreen, next to the rear-view mirror.

The setup requires a special operating system called NeOS and a OnePlus 3 smartphone, the only handset capable of running it. A housing to hold everything in place is then 3D printed and the phone is connected to the car's computer. For now the system only works on the Honda Civic and Acura ILX.

The hacker claims the freely available software will produce the same results as what was shown by Comma.ai earlier in 2016, where a car was shown to drive itself (with Hotz behind the wheel) along a public road.

If an automatic car has both electronic power steering and some form of traction or stability control (which can brake the car) then Hotz says his company can, in the future, make that car autonomous.

Hotz is making a big deal about his software being openly available for anyone to download and experiment with. In a post on the Comma.ai website, Hotz says: "We are releasing some stuff for you. Open stuff. Because we like openness. It's better than closedness... We know we will win [against other self-driving developers like Tesla and Google]. And if you do amazing things with this data, you can join the winning team and do more amazing things with even more data. We love data." Hotz then tells Tesla and Google: "We are waiting for your open releases."

But potential car hackers wanting to make their vehicles autonomous should exercise caution. Hotz describes the software as "alpha quality", meaning it is still very much in the testing and development phase. Demonstrations given to US journalists earlier in the year showed a system which worked, but also became confused and would occasionally stop working, requiring a reboot and for the car to be turned off and on again.

Hotz believes the future of autonomous car development is to teach cars to drive like humans, rather than follow a strict set of rules, and then to learn from what they see every time they drive. A "fleet-learning" system similar to Tesla's, where cars upload their findings to the cloud and share with each other, is also planned.

But for now the Comma.ai software remains entirely experimental and comes with no safety guarantee. As Hotz says: "We're not shipping a product. We're shipping alpha software really for research purposes only. We do not provide any guarantees."