A circular blue sign containing a vertical white arrow pointing upwards instructs drivers that they must proceed straight ahead.
It is installed at junctions where side turning is prohibited to maintain traffic flow, avoid high-risk turn conflicts, or protect one-way street networks.
What this sign means
Vehicular traffic must continue straight ahead; turning left or right at the junction is strictly prohibited.
It acts as a positive mandatory instruction rather than a prohibition sign.
- Vertical white arrow pointing upwards on a blue disc.
- Mandatory requirement to drive straight ahead.
- Bans left and right turns at the intersection.
What to do when you see it
Maintain a central lane position and continue straight through the junction.
Do not activate directional indicators, and do not attempt to turn into side streets at this location.
How this sign is tested
Theory exams test recognition of mandatory directional signs versus informational ahead signs.
Questions evaluate junction diagrams where candidates must identify permitted vehicle manoeuvres.
Common mistakes
Confusing 'Ahead Only' (blue circle) with 'One-Way Traffic' (blue rectangle with 'One Way' text or thick arrow).
Attempting to turn into side streets despite the clear mandatory vertical arrow.
Test yourself on this one
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Practise road sign questionsFrequently asked questions
What is the difference between Ahead Only and One Way signs?
Ahead Only is a circular blue sign instructing you to drive straight ahead at a junction, while One Way (rectangular) indicates a single-direction road.
Can I perform a U-turn at an Ahead Only sign?
No, you must proceed straight ahead without making any turning movements.
Are cyclists exempt from Ahead Only signs?
Cyclists must obey the sign unless a supplementary plate explicitly exempts them.