Is it illegal to drive with hazard lights on in the UK?

In almost all circumstances, yes. The Highway Code states that you must not use hazard warning lights while driving or being towed unless you are on a motorway or unrestricted dual carriageway and you need to warn drivers behind you of a hazard or obstruction ahead, and even then only for long enough to be sure the warning has been seen. Using them in heavy rain, in fog, while crawling in traffic or to say thank you is not permitted. The practical reason is simple: with the hazards on you cannot indicate, so nobody knows what you are about to do.

Can I park on double yellow lines with my hazard lights on?

No. This is one of the most persistent myths in British driving. Hazard warning lamps give you no exemption from any parking restriction — not double yellows, not a bus stop, not a loading bay, not a zig-zag outside a school. Their legal purpose is to warn other road users that a stationary vehicle is temporarily obstructing the road, usually because it has broken down. A traffic warden or police officer will issue a penalty notice regardless of whether the hazards are flashing.

Do hazard lights fail an MOT?

They can. The hazard lamps themselves are inspected with the direction indicators under section 4.4, where a missing, inoperative or wrong-coloured lamp is a major defect, and they must operate with the ignition switched off. The dashboard tell-tale is inspected separately under section 4.9: a missing or inoperative hazard tell-tale is a minor defect, and so is a tell-tale that lights steadily instead of flashing, because the regulations specifically require the hazard tell-tale to be a flashing light.

Why have my hazard lights stopped working when the indicators are fine?

Almost always the hazard switch. On most cars every indicator bulb draws its current through that one switch when the hazards are on, which is roughly double the load the stalk ever sees, and over years the contacts inside pit and burn. The classic symptoms are hazards that work only if you press the button hard, work on one side, or stop working entirely while the stalk indicators are perfect. Switch failure is also why some cars are known for hazards that come on by themselves.

Dashboard warning light

Hazard warning light

Last updated 27 July 2026

Quick answer

The hazard warning lamps are on and all four indicators are flashing together. Nothing is broken. The red triangle is red because it matches the switch, not because it is warning you of a fault — but the rules on when you may use hazards while moving are much tighter than most drivers think.

What to do: No action needed
Can you drive?: Yes

Why it is red

Reserved for hazards and for faults where continuing could injure somebody or destroy something expensive. Most red lamps mean stop, though a few mean the opposite, so read the lamp rather than the colour.

What turns it on

Pressing the triangle switch. On many modern cars the system also triggers itself: emergency braking above a certain deceleration flashes the hazards automatically, some cars flash them after an airbag deployment, and most flash them when the alarm is set off. Hazard lamps are wired to work with the ignition off, which is deliberate — the car may be broken down and unable to run.

What to do about it

Use them when the car is stationary and causing an obstruction, or has broken down, to warn others.
While moving, use them only on a motorway or unrestricted dual carriageway, and only to warn the traffic behind you of a hazard or obstruction ahead. Switch them off once the warning has been seen. That is the only situation in which the Highway Code permits hazards on the move.
Do not use them as an excuse for parking where you should not. Hazard lamps confer no parking rights whatsoever, and a warden or officer will treat the car as illegally parked.
Do not use them as a thank-you flash, and do not leave them on in heavy rain or fog while driving. Both are common, both are prohibited, and both hide your indicators from everyone around you.
If they will not switch off, or work only intermittently, suspect the switch itself. The hazard switch takes the whole indicator current on many cars and its contacts burn.

Can you keep driving?

Yes

The car is fine. The judgement is about when to use them: hazards on the move cancel out your indicators, so a driver using them in traffic cannot signal a turn or a lane change and everyone around them has to guess. Reserve them for a genuine stationary obstruction or a warning to following traffic on a fast road.

What causes it

The hazard switch has been pressed
Automatic emergency stop signalling has flashed them during hard braking
The alarm has been triggered
A sticking hazard switch, which is a common and well-known fault on some models
On a few cars, an airbag deployment or a collision detected by the crash sensor

Does it fail an MOT?

Not on its own — but what causes it often does.

The hazard tell-tale is one of the four mandatory tell-tales inspected under section 4.9.1, but a missing or inoperative indicator or hazard tell-tale is only a minor defect. There is a second, easily overlooked requirement under 4.9.2: the hazard tell-tale must itself be a flashing light, and one that lights steadily rather than flashing is a minor defect. The hazard lamps themselves are tested with the indicators under section 4.4, where an inoperative lamp is a major defect, and they must work with the ignition switched off.

Common questions

Is it illegal to drive with hazard lights on in the UK?: In almost all circumstances, yes. The Highway Code states that you must not use hazard warning lights while driving or being towed unless you are on a motorway or unrestricted dual carriageway and you need to warn drivers behind you of a hazard or obstruction ahead, and even then only for long enough to be sure the warning has been seen. Using them in heavy rain, in fog, while crawling in traffic or to say thank you is not permitted. The practical reason is simple: with the hazards on you cannot indicate, so nobody knows what you are about to do.
Can I park on double yellow lines with my hazard lights on?: No. This is one of the most persistent myths in British driving. Hazard warning lamps give you no exemption from any parking restriction — not double yellows, not a bus stop, not a loading bay, not a zig-zag outside a school. Their legal purpose is to warn other road users that a stationary vehicle is temporarily obstructing the road, usually because it has broken down. A traffic warden or police officer will issue a penalty notice regardless of whether the hazards are flashing.
Do hazard lights fail an MOT?: They can. The hazard lamps themselves are inspected with the direction indicators under section 4.4, where a missing, inoperative or wrong-coloured lamp is a major defect, and they must operate with the ignition switched off. The dashboard tell-tale is inspected separately under section 4.9: a missing or inoperative hazard tell-tale is a minor defect, and so is a tell-tale that lights steadily instead of flashing, because the regulations specifically require the hazard tell-tale to be a flashing light.
Why have my hazard lights stopped working when the indicators are fine?: Almost always the hazard switch. On most cars every indicator bulb draws its current through that one switch when the hazards are on, which is roughly double the load the stalk ever sees, and over years the contacts inside pit and burn. The classic symptoms are hazards that work only if you press the button hard, work on one side, or stop working entirely while the stalk indicators are perfect. Switch failure is also why some cars are known for hazards that come on by themselves.

This is general guidance, not a diagnosis. Manufacturers draw the same system differently and reuse symbols for more than one function, so check the handbook for your own car before acting on anything here.

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