Apple has expanded its autonomous fleet to 27 test vehicles. This latest move from the Cupertino-based tech giant is seen as a bid to significantly advance its self-driving car project in order to catch up to other companies competing in the autonomous vehicle race.

According to Bloomberg, after obtaining a permit to test three autonomous vehicles from the California Department of Motor Vehicles last April, Apple has since registered two dozen more vehicles. The tech giant first added two new cars to their fleet in July followed by seven in October, two in November, six in December and seven just this month.

For its self-driving car project, the tech giant has been using Lexus RX450h SUVs that are equipped with an array of cameras, radars and LIDAR sensors. These add-ons are said to be sourced from third-party suppliers rather than having been developed by Apple themselves.

Apple refused to comment on the expansion of their autonomous fleet, which is not surprising since they have been very secretive about the development and progress of its self-driving project. Since 2015, Apple has been rumored to be developing its own car, codenamed Project Titan. However, it was only in July 2017 that CEO Tim Cook finally confirmed their autonomous plans.

"We're focusing on autonomous systems. It's a core technology that we view as very important," he told Bloomberg at the time.

The Apple executive also confirmed that their efforts would be focused on developing the technology to power autonomous vehicles rather than building the self-driving car. It is believed that in the earlier stages, Apple was interested in developing an actual vehicle but backed out due to anticipated costs of this endeavor.

With regard to the autonomous car race, Apple is seen as lagging behind other companies. One of the major players in this ever-growing segment is Google's Waymo. Apple's perennial rival is already testing around 600 self-driving Chrysler Pacifica minivans in Phoenix and has already brought its autonomous technology to 24 cities.

Meanwhile, General Motors recently sought approval from the federal government to produce and test vehicles without steering wheels and pedals. The automaker stated that the vehicles can be released as early as 2019.

Other automotive companies considered to be ahead of the pack include Ford, Daimler and Volkswagen.