Lane control lights are a kind of traffic signal used to regulate traffic on multi-lane roads and highways. Typically, they authorize or restrict the use of one or more available lanes by means of green lights or arrows (to permit) or red lights or crosses (to prevent) (to prohibit). They are often repeated at regular intervals to give drivers with a constant reminder of the lane status.
One or more lanes on some multilane roadways may be marked as counterflow lanes, indicating that the direction of traffic in such lanes may be reversed at any moment (see also reversible lane). This is sometimes done to manage rush-hour traffic (one or more middle lanes may flow inbound in the morning and outbound in the evening); in other situations, the lanes are reversed only under exceptional conditions (such as a traffic accident or road construction closing one or more of the lanes).
As established by the Vienna Convention on Road Signs and Signs, lane control signals across the globe adhere to a standardized pattern. Typical traffic signals include a green downward arrow that indicates a lane is open to traffic facing the signal, a red cross that indicates a lane is reserved for opposing traffic or closed to traffic in both directions, and a flashing amber circle, arrow, or cross that instructs traffic facing the signal to clear the lane immediately.
Unlike conventional traffic signals, lane control signals feature either a single face to show all lane conditions (the so-called “searchlight” design) or separate faces for each lane situation (as illustrated). This form of lane control signal is often positioned horizontally. There are other signals that indicate various situations for highways without counterflow lanes, such as varying speed restrictions for distinct lanes.