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

Google has been testing self-driving prototypes since 2009, mainly around its Silicon Valley headquarters in Mountain View, California.

Google is sending a second specially equipped Lexus RX450h prototype this week to Austin.

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Last month, the company began testing tiny, bubble-shaped self-driving prototype vehicles of its own design on public roads around Mountain View.

Google and other automotive manufacturers and suppliers have said the technology to build self-driving cars should be ready by 2020.

Google executives have said the company does not want to build its own self-driving cars, but would prefer to find a development and production partner.

Read More: Our Self-Driving Cars Have Never Caused an Accident, Google Says

But most major multinational automakers 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.

A Google press release on Tuesday quoted the Texas Department of Transportation as saying "we welcome and support Google's autonomous vehicle test" in Austin.