What do solid, parallel yellow lines mean on a road?

According to the California Department of Motor Vehicles, solid, parallel yellow lines indicate that vehicles are not allowed to pass. Vehicles are prohibited from driving on the left side of these double solid lines.

California's DMV says that a single solid yellow line means that vehicles to the right of that line are barred from passing. If the yellow line is broken, passing is permitted if the conditions are safe.

The New York State Safety Council states that vehicles are authorized to cross double solid lines if they are making left-hand turns into driveways; however, drivers must yield to other vehicles and may not block traffic flow. Drivers must also use a reasonable speed.