SFR runs three independent Solo series: Bay Area events covered here, and Events from these SFR Chapters:

Sacramento            Fresno

Solo (also called Autocross or Slalom) is a contest of driving skill. We run against the clock (i.e., "solo") on short courses that emphasize car handling and agility rather than speed or power. Speeds and hazards to spectators, participants, and property do not exceed those encountered in normal, legal highway driving. But it is a lot more fun!

In Europe, Autocross is more like our Rallycross.