Declaring "it's no longer a question of if...but when" autonomous vehicles are used in retail, President and CEO of Walmart (NYSE:WMT) U.S. John Furner announced the retail titan's intention to invest in General Motors' (NYSE:GM) Cruise self-driving car company in a press release today. Furner said the move will "aid our work toward developing a last mile delivery ecosystem that's fast, low-cost and scalable."

The Walmart investment brings the total of Cruise's most recent funding round to $2.75 billion, though neither GM nor Cruise provides specifics on how much each individual company contributes to the whole, CNBC reports. Other investors in the subsidiary include GM itself, Microsoft, Honda Motor, and institutional investors. Among other projects, Cruise intends to roll out self-driving taxis in Dubai within the next two years.

Cruise and Walmart began testing self-driving delivery vehicles in Scottsdale, Arizona last November. At the time, Walmart said it picked Cruise because the company could help the retailer reach its 2040 zero-emissions objective, describing the GM subsidiary as "the only self-driving car company to operate an entire fleet of all-electric vehicles powered with 100% renewable energy." In today's press release, after the test has been operating for around 5 months, Walmart says it is "impressed with Cruise's differentiated business model, unique technology and unmatched driverless testing."

While Walmart emphasizes the environmental aspect of its Cruise investment, its mention of "low-cost" last-mile delivery indicates it's looking to control delivery-driver expense in the same way as several restaurant chains are currently investigating robotic delivery vehicles. Domino's Pizza is trying out Nuro's R2 robots to bring pizzas to hungry Houstonians, while Chipotle Mexican Grill invested in Nuro directly.

Self-driving concept cars
Concept autonomous cars from BMW and Daimler BMW/Daimler

This article originally appeared in the Motley Fool.

Rhian Hunt has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Chipotle Mexican Grill and Microsoft. The Motley Fool recommends Dominos Pizza. The Motley Fool has a disclosure policy.