Having obtained a California permit a year ago to test three self-driving cars on the road, Apple has now dramatically increased the number of SUVs in its self-driving test fleet.

Bloomberg’s Alex Webb reported Thursday that the iPhone maker has expanded its California self-driving test fleet to 27 vehicles via an additional 24 Lexus RX450h sport-utility vehicles.

This was confirmed to Bloomberg by the California Department of Motor Vehicles.

The move could indicate that Apple’s secretive self-driving software initiative is progressing well after the company allegedly shut down Project Titan a few years ago and refocused its efforts from car-making fantasies to autonomous driving systems.

Alphabet’s Waymo is already testing its autonomous driving technology in six states, using as many as 600 minivans in Phoenix from Fiat Chrysler Automobiles NV. At the same time, traditional carmakers like Volkswagen and General Motors are adding more self-driving capabilities to their mass-market vehicles already on the road.

According to Tim Cook, Apple has “a large project going” in the self-driving space. “From our point of view, autonomy is sort of the mother of all AI projects,” the CEO said.

“Autonomous systems can be used in a variety of ways, and a vehicle is only one,” Cook added. “There are many different areas of it. I don’t want to go any further with that.”

“We’re making a big investment in this,” Cook said.

Image: Apple’s self-driving Lexus SUV