A five-page letter from Steve Kenner, Apple's director of product integrity, to the National Highway Traffic Safety Administration is the company's most comprehensive statement yet about its interest in self-driving vehicle technology. The Nov. 22 letter followed more than a year of industry speculation about the computer and iPhone maker's plans for expanding into transportation.

"The company is investing heavily in the study of machine learning and automation, and is excited about the potential of automated systems in many areas, including transportation," Kenner wrote.

"Executed properly under NHTSA's guidance, automated vehicles have the potential to greatly enhance the human experience — to prevent millions of car crashes and thousands of fatalities each year and to give mobility to those without."