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.