Green filter arrow: what it means
A green filter arrow lets you go in the arrow's direction if the way is clear, even when the main signal is red.
What does the green filter arrow mean?
A green arrow beside a red light lets you go only in the direction shown, provided the way is clear. In this diagram, that means left. Know your traffic signs explains this combination.
Rule 177 says a green filter arrow applies to a filter lane. Only enter that lane if you intend to follow the arrow, and give other traffic, especially cyclists, room to reach the correct lane.
Quick quiz
What does the picture at the top of this page show?
- Go only in the arrow’s direction, if clear.
- Go straight ahead only.
- Do not turn left here.
Show answer
A. Go only in the arrow’s direction, if clear. A green arrow shown with red allows you to proceed only in the arrow’s direction if the way is clear (Know your traffic signs). Source: Know your traffic signs: traffic signals, GOV.UK; The Highway Code, rule 177, GOV.UK
Where will you see it?
At traffic-light junctions with a filter lane.
What should you do?
Use the filter lane only if you want to go in the arrow’s direction. When the arrow is green, check that the way is clear before proceeding.
What do people get wrong?
A green left arrow does not let you go straight ahead while the main light is red. It allows movement only in the arrow’s direction.
Common questions
Can I turn on a green arrow when the main light is red?
Yes, if the way is clear and you follow the arrow’s direction. Know your traffic signs explains that the green arrow can be shown with red.
Can I use a filter lane to go a different way?
No. Rule 177 says not to enter the filter lane unless you want to go in the direction of the arrow.
Compare with
Green arrow lane control signalThis lane is open to you.
Turn left signYou must go the way the arrow points.
Want to test someone else? Play a road-sign quiz with friends and family.
Sources
Checked on 5 November 2026 against Know your traffic signs (traffic signals) and The Highway Code rule 177.
Contains public sector information licensed under the Open Government Licence v3.0. The diagram is our own simplified drawing, not to scale. Sources and image credits.