US-based autonomous driving technology Waymo, a spinoff from internet conglomerate Alphabet, received $750m in extension equity financing, taking its round to $3bn.

The round was already backed by its parent company Alphabet, automotive component manufacturer Magna International and car retailer AutoNation.

Financial services and investment group Fidelity participated in the extension as did accounts advised by T Rowe Price, Perry Creek Capital and a range of unnamed new backers. Waymo had already raised an initial $2.25bn tranche in March, featuring the three corporate backers as well as venture firm Andreessen Horowitz. The first close was co-led by Silver Lake, Canada Pension Plan Investment Board and Mubadala Investment Company, the sovereign wealth fund of Abu Dhabi. This was the first external capital round for Waymo.

Founded in 2009 as part of Alphabet (then Google) and officially spun off in 2016, Waymo develops a unified autonomous vehicle which aims to combine internally developed technology in areas like cameras and lidar sensors as well as versions of traditional automotive systems covering functions such as brakes and steering.

Waymo is part of the broader autonomous vehicle space, which has received much attention by the general public – after the spectacular performance car manufacturer Tesla’s stock earlier this year – and also by corporate investors. 2015 registered the record number of corporate-backed rounds in these enterprises (63), while last year witnessed the largest amount of estimated total capital ($6.71bn) spread over 51 deals.