Apple has expanded its California fleet of self-driving vehicles from three registered last April to 27 as of early 2018, according to a new report posted by Bloomberg today and sourced from emails with the California Department of Motor Vehicles.

Following the first three vehicle registrations, from July 2017 to January 2018 Apple has registered 24 more Lexus RX450h sports utility vehicles in California as part of its self-driving tests. The company is believed to be "accelerating" efforts to catch up to one of the current leaders in the self-driving field, Alphabet's Waymo.

One of Apple's previous self-driving Lexus vehicles spotted on the road last year

We're focusing on autonomous systems," Cook said in an interview on Bloomberg Television. "It's a core technology that we view as very important." "We sort of see it as the mother of all AI projects," Cook said in his most detailed comments to date on Apple's plans in the car space. "It's probably one of the most difficult AI projects actually to work on."

Work on the "Apple Car" began circulating in rumors from early 2015 , when reports of "Project Titan" emerged and pointed towards upwards of 1,000 employees working on developing an electric vehicle at a secret location near the company's Cupertino headquarters. Over time, the project pivoted away from Apple constructing a vehicle of its own to the development of a self-driving software system, which CEO Tim Cook confirmed last summer.

Now, Apple is said to be gearing up to compete with Waymo and its self-driving tests, which have currently expanded into six states, encompassing 600 minivans in Phoenix, Arizona alone and now open up to public applicants. Waymo partnered with Lyft last year to begin building a ride-hailing service that aims "to bring autonomous vehicle technology into the mainstream," and then began testing such a service without a safety driver "or any human at all" behind the steering wheel.