What do Solid Yellow Lines mean?

Yellow lines of all types indicate the leftmost edge of where you can drive in a certain direction.

A double solid yellow line may not be crossed except when making a left-hand turn to either leave or join the road divided by said line. A single yellow line on a two-lane, two-way road serves the same purpose.

Some jurisdictions use yellow lines on one-way roadways or divided highways to indicate the left edge of the roadway.