Tesla Model S Autopilot
Autopilot takes control of the steering, accelerator and brakes of all new Tesla Model S carsReuters

Starting today, 15 October, and continuing over the coming weeks, all Tesla cars bought in the past 12 months will receive an over-the-air software update giving them the ability to drive autonomously. Called Autopilot, the feature will let the cars accelerate, brake, steer, change lanes and park themselves.

Tesla chief executive Elon Musk announced the new features in his usual charismatic way, but with a degree of hesitation. Although the system can drive the car on motorways and roads where there are clear lane markings without any human input, Musk suggests drivers keep their hands – or at least a little finger – on the wheel at all times. But future technologies should allow for full autonomy, the 44-year-old said.

'It will be way better than a person'

"The driver cannot abdicate responsibility. That will come at some point in the future," Musk said, adding that the system, which uses cameras and radar, will learn and improve over time. "Essentially it's like a person – how well can a person figure out what route they should take. Over time it will be better than a person. Long term it will be way better than a person. It never gets tired, it's never had anything to drink, it's never arguing with someone in the car. It's not distracted."

By monitoring torque subjected to the steering wheel, the system knows if the driver is not touching the wheel at all. A beep sounds and the car's display panel instructs the driver to remain in contact with the wheel. If they fail to do so, the car will sound an alarm; if the driver still does not take back control, the car will brake slowly to a stop and switch on its hazard warning lights. Drivers are told to sit with their arms on their legs, palms up, with fingertips lightly touching the wheel.

Elon Musk
Tesla CEO Elon Musk says Autopilot will learn to become better at driving than humansReuters

The system works best at speeds above 18 miles per hour, but can take the car down to a crawl in heavy traffic, providing there are clear lane markings and enough other vehicles around for it to follow. Changing lanes is done by flicking the indicator stalk. Drivers are told to check their blind spot as they would normally, but the car will also check and refuse to pull out until its path into the next lane is clear.

If the car is unsure about what to do, such as at a junction where road markings disappear, or in heavy rain and snow where lines are hard to see, it will give control back to the driver.Control can be taken back manually by touching either pedal or turning the steering wheel.

Exercise caution

Musk said: "We tell drivers to keep their hands on the wheel just in case, to exercise caution to begin with. Over time, long term, you won't have to keep your hands on the wheel – we explicitly describe this as beta." The system also recognises pedestrians and reacts if they step out. "It should not hit pedestrians, hopefully," Musk said. "It should handle them well." Despite having a more advanced level of autonomy than other cars on the road, the driver remains liable for any collisions the Tesla is involved in.

As for a global roll-out, Tesla says this will happen worldwide over the coming weeks and months, although in some countries this will require changes in road and traffic laws. Musk said: "Regulators need to see clear evidence that the reliability is there. It works almost to the point where you can take your hands off, but we won't say that. Almost."