There has been a considerable amount of speculation surrounding Apple's interest in creating a car and while the company has largely been silent about the venture, a letter from Apple to the National Highway Traffic Safety Administration (NHTSA) appears to confirm its exploration of the idea.

The five-page letter, from Apple director of product integrity Steve Kenner, was sent to offer comment on the United States government's attempts to lay a policy foundation for self-driving cars on roads across the country. Also revealed in the letter, though, is the strongest clue yet that Apple is planning to get into the car business.

“Apple uses machine learning to make its products and services smarter, more intuitive, and more personal. 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

There is little detail in the letter in terms of Apple's future plans, but it does mark a rare public acknowledgement of the company's long-rumored interest in automotives.

Apple has ramped up what appears to be its efforts to either build a car or create its own autonomous system for vehicles. The company began building a “software core" that will act as the basis for a car's self-driving functionality.

The Wall Street Journal reported Apple has hundreds of engineers working on a vehicle, dubbed Project Titan, in an effort to challenge Tesla in the electric car market. The Cupertino company also reportedly hired a former Tesla executive  to lead its automotive initiative. 

Elon Musk, CEO of Tesla, called Apple's project an "open secret" earlier this year and said it would be a "more direct" challenge to Tesla than other tech companies exploring self-driving vehicle technology, indicating Apple is building its own vehicle and not just an autonomous system.

Apple encouraged the NHTSA to implement guidance for self-driving vehicles, both in hopes of providing rigorous safety principles for design and production as well as to expedite the process of getting the cars on roadways. The company asked for the regulatory body to work toward the goal of "fostering innovation, improving regulatory flexibility, and encouraging the development of life-saving technology" in its decision-making.

The friendlier those rules are toward autonomous vehicles, the sooner one with an Apple logo on it may be on the road.