Driving for two
From the CHP FAQ:
I'm pregnant. The HOV lane requires two persons in a vehicle. Now that I'm eating for two, can I use this lane?
California law requires that in order to utilize the HOV lane, there must be two (or, if posted, three) separate individuals occupying seats in a vehicle. Until your "passenger" is capable of riding in his or her own seat, you cannot count them.
You hear that Bush and Supreme Court? California law enforcement says it's not a "person" until it's riding in a seat next to you. This will probably bum out all the Christians in the house. Further insult to injury is I'm betting you won't get out of a ticket by claiming Jesus as your co-pilot, either.