Signals 10/ 15
California

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Special lights above the pavement are sometimes used to indicate which lanes of a highway can be used at given times:
Steady red “x”: do not drive in this lane.
Steady yellow “x”: move from this lane.
Flashing yellow “x”: this lane can be used for a left turn only.
Green arrow: you are allowed to use this lane.

Reversible Lanes.
Some travel lanes are designed to carry traffic in one direction at certain times, and in the opposite direction at other times. These lanes are called “reversible lanes” and are usually marked by double-dashed yellow lines.

Before you start driving in them, check to see which lanes you can use at that time. There may be signs posted by the side of the road or overhead.
Special lights are often used. A green arrow means you can use the lane beneath it; a red “X” means you cannot. A flashing yellow “X” means the lane is only for turning. A steady yellow “X” means the use of the lane is changing and you should move out of it as soon as it is safe to do so.