You may cross over a solid yellow line to make a left turn at an intersection, to enter or exit a road or a driveway, or to make a U-turn, if it can be made safely and is not otherwise prohibited.

A diamond yellow sign with an arrow going one way, and another line going through an arrow, tells the driver:

The shape of a circle is commonly used in California for advance warning that means there is a railroad crossing ahead.

The sequence of most traffic lights in which they are lighted is red to yellow, yellow to red, and red to green.

The shape of a pentagon is used to indicate:

A center traffic lane enclosed by double yellow lines on each side with the inner lines broken may be used to start and complete left hand turns and start U-turns from either direction of traffic, but cannot be used for passing.

An equilateral triangle shaped sign pointed down means:

When you see a yellow light, you should slow down and stop before entering the intersection, if you can do so safely.