A solid yellow “X” over a traffic lane means:

Lane use control signals are used when the direction of the flow of traffic in a specific lane changes throughout the day. They are used to show which lanes of traffic are open and closed, as well as to show if toll booths are open or closed. A signal displaying a solid yellow “X” means that drivers must move out of the indicated lane because it is about to be used by oncoming traffic.
DMV Writen Test