California's Move Over law requires:

If an emergency vehicle with its lights on is stopped on the side of the road, California drivers are required to vacate the lane directly next to the vehicle, if possible. If a driver cannot move over safely, they must slow down and proceed with caution. This law also applies when approaching a stopped tow truck or Department of Transportation vehicle.

• All vehicles to stay in the right lane at all times.
• Trucks to use the left lane.
• All vehicles to vacate the lane closest to an emergency vehicle that is stopped with its lights flashing.