There’s a lot of money being poured into the self-driving space right now. Building a robot driver capable of fully replacing a human on the wheel is a mission that has everything that Silicon Valley loves: a lot of tech and a huge potential prize. Tradition has it that you have to win the race to take any of the prize. But companies are increasingly realizing that they might not get there alone. To see what that means in practice, Marketplace’s Jack Stewart took a trip to Arizona, where several companies are taking advantage of the state’s welcoming regulatory attitude toward self-driving testing.