What do blue circular road signs generally tell me?

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Blue circular signs give a mandatory instruction: they tell you something you must do, such as turn left, keep left, or follow a route that is only for buses and cycles. Red circles do the opposite – they tell you what you must not do.

The quick rule for the theory test

• Blue circle = you must (a positive instruction).
• Red circle = you must not (a prohibition, e.g. no entry, no U-turn, a speed limit).
• Red triangle = a warning of a hazard ahead.
• Rectangle = information or directions.

Common blue circular signs

• Turn left / turn right ahead
• Keep left (or keep right) – usually at a traffic island
• Mini-roundabout – give way to traffic from your right
• Route for buses and pedal cycles only, or a segregated route for cycles and pedestrians
• Minimum speed – you must not drive slower than the number shown, unless it is unsafe

Watch out for the exceptions

A blue circle with a red border and a red diagonal line is not an instruction to do something – it means no waiting. With a red cross it means no stopping (clearway). These come up often in the theory test because they break the “blue means must” rule.

Also remember that blue rectangles are different: on motorways they give directions, and elsewhere they give information such as a one-way street or a parking place.

Want to test yourself? Try our road sign flashcards or the road sign quiz, and see the full guide in the Highway Code traffic signs.