Usage of NASCAR trademarks, hosting videos, and even linking to the video on their homepage.
I'm more inclined to believe that it's real. But I've fallen for more Google April Fool's jokes then I'd care to admit.
direct mp4 w/o ads.
Update Apr 1, 10:05 a.m.: As you probably guessed—no, Google Racing isn’t real. We were really happy to work with NASCAR on this April Fools' joke. The technological advancements this sport has made in the last decade are impressive and while we won’t be providing self-driving cars to compete in the races, we look forward to working together with NASCAR in the future on projects like their YouTube channel. What better way to drive change?
Which is exactly what computer are great at. What they are terrible at is dealing with incomplete information.
A computer would actually make a great race car driver.
Edit: I would totally pay to see autonomous robots race on a track without the limitations of human drivers.
I've actually driven on a track (once) and it's surprisingly different/difficult.