Ironically racing is probably a better defined operating environment so easier to successfully automate.
I work for a company that automates vehicles (ASI). We specifically target controlled operating environments like vehicle proving grounds, mines, and commercial harvesting operations. These places all have one thing in common: ten foot fences (aka, no toddlers in the vicinity).
The biggest struggle we have had is obstacle detection; it only works at distances less than 50m. The various vision devices aren't accurate enough beyond that range (or get lost in smoke, fog, dust, shakiness, etc.) And differentiating small objects (aka, 20cm cube) from standard terrain is neigh impossible with current technologies. The algorithms used to process that information can't run in real-time on embedded hardware.
I'm excited for a lot of recent progress in electronic vehicle control. Look for your favorite auto-manufacturer to introduce electronically controlled steering, transmissions, and throttle over the next few years. The pedals, knobs, and wheels will soon be fancy computer joysticks.