A circular blue sign displaying a white arrow pointing diagonally or horizontally left orders drivers to turn left ahead.
It is placed in advance of one-way entry points, dual carriageway junctions, or restricted intersections where continuing straight or turning right is illegal.
What this sign means
Drivers must make a left turn at the upcoming intersection.
Proceeding straight ahead or turning right is strictly prohibited.
- White arrow pointing left on a blue circular background.
- Mandatory instruction to turn left ahead.
- Prevents wrong-way driving onto one-way systems.
What to do when you see it
Signal left in good time and move into the left lane smoothly.
Slow down as you approach the junction and complete the left turn safely.
How this sign is tested
Theory test items assess knowledge of mandatory blue circular signs.
Questions ask candidates to choose the correct driving action when approaching this sign on a multi-lane road.
Common mistakes
Confusing 'Turn Left Ahead' (blue circle) with 'No Right Turn' or 'Keep Left' bollard signs.
Failing to signal left prior to completing the mandatory turn.
Test yourself on this one
Road and traffic signs is the biggest category in the question bank with 102 questions, and signs turn up inside other categories too. Work through them free, no sign-up needed.
Practise road sign questionsFrequently asked questions
When should I turn left after seeing this sign?
Turn left at the immediate junction located directly ahead of the sign.
Can I go straight ahead if no traffic is coming?
No, proceeding straight ahead violates a mandatory order-giving traffic sign.
What shape are mandatory instruction signs?
Mandatory instruction signs in the UK are circular with a blue background.