Tech giant Apple has joined the list of companies approved to test driverless vehicles on California's roads.

As of 13 April 2017, Apple is permitted by the state's Department of Motor Vehicles (DMV) to test its self-driving car technology – along with rival tech companies Google, Zoox and Drive.ai, as well as car brands like BMW, Ford, Mercedes Benz and Tesla.

This will allow the company to move forward with Project Titan – its autonomous vehicle project – which it has reportedly been working on for years.

Apple officially announced its intensions for entering the self-driving transport market in a letter to US transport regulators in December 2016.

Rumours that the company was developing an electric car emerged back in 2015, but rather than designing a vehicle itself, Apple now appears to be focussed on creating autonomous driving software that could be used by various auto brands.

This also seems to be the approach being taken by Google, which rebranded its self-driving vehicle division as a new company called Waymo late last year and unveiled a partnership with Chrysler shortly after.

BMW board director Peter Schwarzenbauer voiced his suspicions that both companies were changing tack during an interview with Dezeen earlier this year.

"I'm not sure [Apple and Google] are going to build cars [themselves] but it seems that they are moving towards a kind of mobility concept," he said. "They are trying to offer a mobility ecosystem that is part of their 'connected life' approach."

California's roads are already filling up with driverless vehicles. Last month, the DMV revealed a set of proposed regulations designed to pave the way for developers to move forward with their plans.

Beverly Hills unanimously approved plans for a driverless-car programme that could replace the affluent Los Angeles neighbourhood's public transport system.

Tesla, Uber and Google have all tested their autonomous cars on the state's public roads, although Uber's were ordered off San Francisco's streets hours after launch and one of Google's vehicles was involved in a collision.