California have what they call a Ambulance Certificate. Basicly all it is another endorsemant on your drivers license.
To get one you have to have a physical, just like with a CDL, then you trip on down to your local "live scan" agency to get your fingerprints taken. After that you take all that paperwork down to the DMV, who administer a written test. If you pass said written test you get issued with a small slip of paper which says you can legally pilot a Ambulance through the busy streets of
California. Simple......time consuming and expensive