Green arrow lane control signal: what it means
A green arrow pointing down at a lane control signal means the lane below is open to traffic facing it.
What does the green arrow lane control signal mean?
Know your traffic signs says lane control signals above the road show which lanes are available: a green arrow means the lane is available to traffic facing the signal. The Highway Code lists it as lane available to traffic facing the sign.
Quick quiz
What does the sign at the top of this page mean?
- This lane is closed to you.
- The lane closes ahead: move to the next lane.
- This lane is open to you.
Show answer
C. This lane is open to you. A green arrow means the lane is available to traffic facing the signal (Know your traffic signs). Source: Know your traffic signs: tidal flow lane control signs and signals, GOV.UK; The Highway Code: light signals controlling traffic, GOV.UK; Traffic sign images, Department for Transport, GOV.UK
Where will you see it?
Above lanes on busy roads where the number of lanes in each direction changes, often called tidal flow.
What should you do?
You may use the lane. Keep watching the signals, as they can change.
What do people get wrong?
Thinking the arrow tells you to change lanes. A downward green arrow just means the lane is open.
Common questions
What is tidal flow?
Lane control signals change the number of lanes in each direction to give priority to the main traffic flow.
What do the other signals mean?
A red cross means the lane is closed; a white diagonal arrow means move to the next lane in the direction shown.
Compare with
Red cross lane control signalThis lane is closed to you.
White arrow lane control signalThe lane closes ahead: move to the next lane.
Want to test someone else? Play a road-sign quiz with friends and family.
Sources
Checked on 4 November 2026 against Know your traffic signs (tidal flow lane control signs and signals) and The Highway Code (light signals).
- Know your traffic signs: tidal flow lane control signs and signals, GOV.UK
- The Highway Code: light signals controlling traffic, GOV.UK
- Traffic sign images, Department for Transport, GOV.UK
Contains public sector information licensed under the Open Government Licence v3.0. Traffic sign images are Crown copyright, from the Department for Transport. Sources and image credits.