Apple is working on a self-driving car, and is currently scouting for secure locations in the San Francisco Bay area to test its designs, with newly revealed documents suggesting the project is much further along than previously thought.

According to documents obtained by the Guardian, engineers from Apples Special Project group began scouting locations in May, focusing on GoMentum Station, a former naval base near San Francisco that is being turned into a high-security testing area for autonomous cars.

The base, which have over 20 miles of paved highways and mocked-up city streets, has already been used by Mercedez-Benz and Honda for tests with self-driving cars, and is supposedly the worlds largest secure test facility for autonomous vehicles.

Rumours of Apples self-driving electric car, codenamed Project Titan, have been circulating for a while, but this is the first time documents have confirmed its existence, and suggest that Apple is almost ready to begin road-testing.

Tim Cook, CEO of Apple, has met with executives from various car manufacturers in recent months, including Fiat-Chrysler CEO Sergio Marchionne, and the company has been recruiting experts from established automotive companies such as Tesla Motors and Mercedes-Benz.

Apple has not commented on any plans it may have, but with Jeff Williams, senior vice president of operations, calling cars “the ultimate mobile device” at a conference in May, there can now be little doubt that Apple is planning on entering the automotive market.