A new clue about Apple's work on autonomous driving technology has emerged in the form of a scientific paper authored by two of the company's engineers, as Reuters first noticed.

Why it matters: Apple is notorious for its secrecy and while rumors floated for years that it was working on an automotive project, its interest in the area wasn't confirmed until it obtained a permit to test self-driving cars in California earlier this year. This new paper is a departure from Apple's secretive culture in that it reveals some of the technological approaches it's developing.