Cruise, the autonomous driving unit of General Motors, has added an additional $750 million to a previous $2 billion funding round.
The top-up corporate round comes via unnamed "institutional investors" and U.S. retail giant Walmart.
In January this year, Microsoft led a $2 billion funding round as part of a long-term strategic relationship to accelerate the commercialization of self-driving vehicles.
The latest injection of capital brings the total placed in the company to $8 billion over ten rounds.
Cruise's CEO Dan Ammann concedes that the vision for the company requires "a lot of capital" alongside talent and partnerships.
He adds: "Self-driving cars will make transportation safer, cleaner and more accessible for everyone."
In late-2020, Walmart and Cruise struck a deal to launch a self-driving delivery pilot using all-electric fleet in Phoenix, Arizona.
Walmart president and CEO John Furner says: "This investment is a marker for us – it shows our commitment to bringing the benefit of self-driving cars to our customers and business."
Last month, Cruise acquired Voyage, a developer of technology for self-driving cars.
Terms of the deal were not disclosed.
Voyage brought Commando, its self-driving artificial intelligence, Shield, its collision mitigation system, and Telessist, its remote assistance solution, to the Cruise platform as part of the deal.