San Francisco Region uses the RTP/PAX index, with the addition of entries for OSP and BSPV which are SFR Regional classes and therefore do not have RTP/PAX indexes (see table). We use this index for

• Street Tire Classes
• Indexed Order of Finish and Top Time of Day

The RTP/PAX index is a system of handicapping cars, so that drivers in different SCCA classes can compare times against each other maintained by Rick Ruth.  Info about it is maintained at
 www.scca-chicago.com/solo/indexes

"This Index was developed by Rick Ruth and reflects results from over 30 large events including the Tire Rack® Solo II National Championships, National Tour, Subaru CenDiv, Chicago Region SCCA, Tri-State Sports Car Council and Wisconsin Autocrossers Inc events."

The RTP/PAX index for the fastest class (AM) is always 1.0. For any other class, multiply your time by the index for your class to get the time you theoretically would have run in an AM car. 

History

The PAX Index was an earlier system of handicapping cars.  John Kelly tells us it was invented by Jim McKamey for a series of autocrosses he ran at one time, and then was updated each year by Dave Beck. 

The RTP index was a separate set of indexes, calculated from different events, but basically similar.  They used to be separate in any case, but starting in 2002 Dave Beck no longer maintained the PAX index, and Rick Ruth combined and enhanced them into the RTP/PAX index.

2009 SFR Handicap Index

Based on Rick Ruth's reference table.
Thank you Rick!!