Google has begun testing its self-driving cars in Austin, Texas, hoping to gather information on how the prototypes interact with traffic, road conditions and people.

Google has been in the self-driving car game since 2009, testing the cars mainly around its Silicon Valley headquarters in Mountain View, California. Google, along with other carmakers, hopes the technology will be ready by 2020.

Google is sending a second specially equipped Lexus prototype this week to Austin. In June, the company began testing tiny, bubble-shaped self-driving prototype vehicles of its own design on public roads around Mountain View.

But most major multinational carmakers are developing their own so-called 'automated vehicles' that are designed to control major functions such as steering, brakes and throttle without human effort.

The Google self-driving cars have humans on board who can assume manual control of the vehicles if necessary.

Both Google and Apple maintain offices in Austin, an emerging technology hub in the south west of the US.