Lane control signals

Lane control signals hang over individual lanes and say whether that lane is open to you right now. They exist because some lanes change direction during the day — a lane that carried you into the city this morning may be carrying traffic the other way tonight.

• Green arrow — drive in this lane.
• Red X — do not drive in this lane.
• Flashing yellow X — move out of this lane and into one showing a green arrow.

One case is worth memorizing separately: if the signals over all the lanes are flashing yellow, slow down and proceed with caution rather than hunting for a green arrow that is not there.

On the road surface, a reversible lane is marked by double broken yellow lines. Seeing those lines is your cue to look up.