You can enter or exit the carpool lane when?

Answer 1

Entering and exiting the carpool lane on the freeway is regulated by the type of line on the right hand side of the lane. The driver can enter or exit the lane only when the lane is not bordered by a white solid line.

Answer 2

You can enter or exit the carpool lane when the white line is dotted or solid. However, although legal, it is discourage when you cross the solid white line. In fact, in some places there is a gap between the carpool lane and the freeway when there is a solid white line to prevent you from entering or exiting. Even more so, sometimes the solid white line is neighbored or replaced by a double yellow line, which you cannot cross.