When are you allowed to use hazard warning lights?

A: When stopped and temporarily obstructing traffic

B: When travelling during darkness without headlights

C: When parked on double yellow lines to visit a shop

D: When travelling slowly because you're lost

You mustn’t use hazard warning lights while moving, except to warn traffic behind when you slow suddenly on a motorway or unrestricted dual carriageway.
Never use hazard warning lights to excuse dangerous or illegal parking.

You may also be interested in these theory test questions

While you’re driving, a warning light on your vehicle’s instrument panel comes on. What should you do?

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You’re at the scene of an incident. Someone is suffering from shock. How should you treat them?

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What should you carry for use in the event of a collision?