All I know is they are marked with a diamond and you aren't supposed to drive in them unless you have 2 or more people and/or you are traveling "through" the city. I must admit that some places that I have driven through that had these diamond lanes, I had merged over the solid lines, but I never made a maneuver that would be considered unsafe or erratic. Now that I know about the breaks, I suppose I will use them next time. ;)