State Child Restraint Required : Younger than 1 yr. or less than 20 lbs. or in a rear-facing restraint system in rear seat only if front pass. air bag is active. 5yrs. and younger or less than 60 lbs. in a rear seat
Adult Safety Belt Permissible : 6 through 15 yrs. or 60+ lbs.
Max. Fine 1st Offense : $100.

Graduated Licensing Laws

Learner Permit Min. Age : 15 yrs. 6 months
Intermediate Minimum Age : 16
Full License Minimum Age : 16 yrs. 6 months

Older Driver Laws

General population length of renewal : 5 years
Provisions for older drivers : No renewal by mail for drivers 70 and older

 
School buses -- when you come to a school bus stopped on either side of a road with the bus's red lights flashing, you must stop, and remain stopped as long as the red lights are flashing. These laws are strictly enforced in some places, not in others.

Californian school buses are immediately recognizable -- they're the same as elsewhere in the US, i.e. special yellow buses clearly marked "School Bus" on the front and rear (at least).

If you're a foreigner you've probably seen them on TV or in the movies -- they're an inescapable part of life here. The flashing red lights on the bus mean that children are getting on or off the bus and are likely to try to cross the road near the bus.