Apple has written to the US’ National Highway Traffic Safety Administration, confirming its interest in developing autonomous vehicle technologies.

It is the tech giant's biggest signal yet that it is indeed developing either its own self-drive hardware, or software that may be used by other autonomous car makers.

Apple revealed it was "investing heavily" in automation, adding that it was “excited by the potential of automated systems in many areas, including transportation”.

The letter notes potential "societal benefits" of self-drive cars, which in theory could dramatically reduce the number of crashes on roads worldwide.

The letter falls short of admitting that Apple is working on a self-drive car, but does address regulatory and ethical challenges it views as hindering the development of autonomous technologies.

Crash and near-miss data should be shared by self-drive car developers, according to Apple, because it would lead to a "more comprehensive dataset than any one company can create alone”.

However, the letter also said that individual’s privacy should not be put at risk by the sharing of such data.

A recent Bloomberg report stated Apple’s self-drive car projects were on hold and that it may be refocussing on developing autonomous software for other car makers.

A number of other firms are working on self-drive cars, including Ford, which says it will have an autonomous car on the road by 2021.

Electric carmaker Tesla is also working on automated systems, while Google has been testing autonomous cars in California for some years.

Notoriously secretive about its forthcoming projects, Apple’s decision to write a letter to the NHTSA is a clear signal that it is already moving into autonomous tech – although the tantalising prospect of an Apple Car is not yet certain.