Tesla's new autopilot system lets electric car change lanes by itself

Company excited about semi-autonomous system but warns that drivers will still have to keep their hands firmly on the wheel

The electric carmaker Tesla Motors hopes to overtake competitors with a new autopilot system that lets cars change lanes by themselves.

Like other semi-autonomous systems available from companies including Mercedes, Audi and Volvo, Tesla's system automatically keeps the car within its lane and maintains a certain distance from the car in front, both at highway speeds and on city streets.