Hazard warning lights are one of the most misused controls on Irish roads. On any given day in Ireland you will see cars using them in heavy rain while moving, stopped at junctions with hazards on, parking illegally with hazards flashing as if they grant immunity, and occasionally — correctly — warning of danger on a motorway. Only one of those uses is appropriate. The hazard light button is a safety device with a specific purpose, and using it incorrectly doesn't just break the rules — it actively creates the hazards it is supposed to warn about.

Source & Credit: Based on the Road Traffic Act 1961 (as amended), Road Traffic (Lighting) Regulations, RSA Rules of the Road (Section 6: Lights on Vehicles), and RSA driving test secondary control requirements. Official resources at rsa.ie. BP Driving School is an RSA-approved ADI in Swords, North Dublin.
Note: Irish road traffic law on lighting is set out in the Road Traffic (Lighting) Regulations. This guide summarises the practical application of those rules. For specific legal queries, consult a qualified Irish solicitor or the official RSA Rules of the Road publication.
Driving Emergencies & Breakdowns — Article Series
In This Guide
  1. What Hazard Lights Are For
  2. When You Should Use Them
  3. When You Must Not Use Them
  4. Quick Reference — Use / Don't Use
  5. The Motorway Moving Exception
  6. Why Rain Is Not a Valid Reason
  7. Hazards and Illegal Parking
  8. Hazards Disable Your Indicators
  9. Hazard Lights on the RSA Driving Test
  10. How to Operate Hazard Lights
  11. The Most Common Misuses in Ireland
  12. Frequently Asked Questions

What Hazard Lights Are For

Hazard warning lights exist for one primary purpose: to communicate to other road users that your vehicle is a hazard — either stationary and unable to move, or (in one specific situation) that there is sudden danger ahead on a fast road.

The RSA Rules of the Road describes hazard warning lights as a device to be used "when your vehicle is a temporary obstruction" — the core principle being that the vehicle itself is creating a danger that other road users need to be warned about. They are not a general-purpose communication tool. They are not a courtesy signal. They are not a parking permission device.

Hazard Lights — Correct Purpose vs Common Irish Misuses
Hazard lights correct use — broken down vehicle, collision scene, motorway queue warning — versus incorrect use — rain, junctions, illegal parking, thanking other drivers ✓ Correct Uses 🚨 Broken down / vehicle is an obstruction 🚗 After an accident — at the scene 🛣 Motorway — warning of sudden queue ahead 🚚 Abnormal or oversized load vehicle ✗ Incorrect Uses 🌧 Driving in heavy rain or fog 🚦 Stopped at junctions or traffic lights 🅿 Parked illegally "just for a minute" 👋 Thanking another driver for letting you out
Four correct uses of hazard lights in Ireland (left) versus four of the most common incorrect uses (right). The incorrect uses are all widespread on Irish roads — all are wrong and several are actively dangerous.

When You Should Use Hazard Lights

There are a small number of situations where hazard lights are the correct response. In each case the underlying condition is the same: your vehicle represents a hazard to other road users and you need to communicate this immediately.

✅
Broken down on a live road

When your car has broken down and is stationary on a road — particularly a fast road, a main road, or any position where it may not be expected by approaching drivers — hazard lights must be on immediately. This is their primary purpose. Leave them on until recovery arrives or the obstruction is cleared. A warning triangle (where safe to place one) supplements but does not replace hazard lights.

✅
After a road traffic accident

After any collision on a road, switch on hazard lights immediately to warn other approaching road users. Both vehicles involved (if driveable enough to do so) should have hazards on. This reduces the risk of a secondary collision involving approaching traffic that has not yet seen the scene.

✅
Motorway or dual carriageway — warning of sudden danger ahead (while moving)

This is the one permitted situation where hazard lights may be used while the vehicle is moving. See the dedicated section below for the full rules and technique. This applies specifically to warning of an unexpected queue or danger ahead on a fast road — not general motorway driving.

✅
Abnormal load or oversized vehicle

Vehicles carrying abnormal loads — oversized agricultural machinery, wide loads on transport trucks — are required to display hazard lights as a warning of their unusual size and the potential obstruction they create for following and oncoming traffic.

✅
Stopped on a hard shoulder in an emergency

When stopped on a motorway hard shoulder after a breakdown or emergency, hazard lights should be on continuously. They should remain on throughout the time the car is in that position — not just briefly. Combined with a reflective triangle (where it is safe to place one without walking on a live motorway), they maximise visibility to approaching traffic.

When You Must Not Use Them

Incorrect use of hazard lights is extremely common on Irish roads. Every misuse listed below is either directly unsafe or creates confusion that leads to unsafe behaviour from other road users.

❌
While driving in heavy rain or poor visibility

The single most common misuse in Ireland. Hazard lights while moving in rain disable your direction indicators — other drivers cannot tell which way you intend to turn or whether you are changing lane. They do not increase your visibility to following traffic more than properly used dipped headlights. The RSA instruction for rain is clear: use dipped headlights. See the dedicated section below.

❌
Stopped at traffic lights or junctions

Stopping at a red light or a junction does not make your car a hazard. Every other driver expects vehicles to be stopped at traffic lights. Using hazards here prevents you from signalling when you move off and creates unnecessary confusion for following drivers about your intentions. Simply brake and wait.

❌
While illegally parked — "just for a minute"

Hazard lights do not exempt a vehicle from parking restrictions. A car on double yellow lines with hazards flashing is still illegally parked and still liable for a fixed charge and penalty points. An Garda Síochána and local authority traffic wardens will issue penalties regardless of whether hazards are on. See the dedicated section below.

❌
As a "thank you" to another driver

Many Irish drivers give a brief double-flash of hazards to thank another driver who let them out or gave way. While well-intentioned, this creates genuine confusion — a brief flash of all four indicators in an unexpected context can be misread as a vehicle emergency by following drivers. The correct acknowledgement is a hand wave or a brief nod — not hazard lights.

❌
When driving slowly for any reason — school runs, looking for parking

Driving slowly while looking for a parking space, proceeding carefully through road works, or navigating an unfamiliar area does not justify hazard lights. You are not an obstruction — you are a slow-moving vehicle. Other drivers can see you. Use normal driving behaviour and position, not hazard lights.

⚠
Being towed — context-dependent

A vehicle being towed is an unusual situation that may benefit from hazard lights on the towed vehicle to communicate its status to following drivers. However, towed vehicles cannot signal, so the hazard lights serve a useful warning purpose. Check that your hazard light system is working before towing — on some cars the hazards will not operate if the car is not running.

Quick Reference — Use / Don't Use

✓ Use hazard lights when…
  • Your car has broken down on a live road
  • You are stopped after an accident on a road
  • You are on a motorway hard shoulder in an emergency
  • You need to warn of sudden queue/danger on a motorway while moving (brief only)
  • You are an abnormal load vehicle
  • You are being towed on a live road
✗ Do not use hazard lights when…
  • Driving in rain, fog or reduced visibility
  • Stopped at traffic lights or junctions (not broken down)
  • Parked illegally or briefly anywhere
  • Saying thank you to another driver
  • Driving slowly through roadworks or looking for parking
  • Driving through a ford or flood (you need your indicators)
  • Picking up or dropping off a passenger — unless genuinely creating an obstruction

The Motorway Moving Exception

The one situation where Irish road traffic law permits hazard light use while the vehicle is moving is specifically on motorways and dual carriageways, to warn following drivers of a sudden queue, accident, or obstruction ahead that they may not be able to see in time.

The correct motorway hazard light technique:
  • You are approaching a sudden, unexpected traffic queue or accident on a motorway at speed
  • Switch on hazard lights briefly to warn following drivers behind you
  • Apply your brakes progressively to slow for the queue
  • Cancel the hazard lights as soon as the following driver has received the warning — hazards should not be left on throughout a slow queue
  • Once stationary in a motorway queue, hazard lights may be used again if the queue is unexpected and there is a risk of being struck from behind at speed
This is a brief, purposeful use — not a reason to drive the entire motorway with hazards flashing.
Motorway Hazard Light Technique — Warning of Sudden Queue
Motorway hazard light use — car approaching sudden queue activates hazards briefly to warn following driver, then cancels once warning received and decelerates to join queue Traffic queue → Your car — hazards ON briefly Following driver Traffic direction ← Warning transmitted Hazards OFF now braking Direction of travel ←
The correct motorway hazard technique: activate hazards briefly when approaching a sudden queue to warn following drivers, then cancel the hazards as you decelerate to join the queue. Do not drive the entire motorway with hazards on — this defeats the purpose of the warning.
Do not confuse "motorway queue" with "raining on a motorway." The motorway exception applies specifically to sudden, unexpected danger ahead — an accident, a sudden queue, debris on the carriageway. It does not apply to ordinary motorway driving in rain, fog or reduced visibility. For those conditions: use dipped headlights, increase following distance, and reduce speed. Do not use hazard lights.

Why Rain Is Not a Valid Reason to Use Hazard Lights

The hazard-lights-in-rain habit is so widespread in Ireland that many drivers assume it is correct practice. It is not — and understanding why helps break the habit.

Three specific reasons why hazard lights in rain are wrong:
  1. They disable your indicators. While hazards are flashing, your direction indicators cannot be seen by other road users. In heavy rain — exactly the conditions where visibility is already reduced — the driver behind cannot tell whether you intend to turn left, turn right or change lane. This is the opposite of safer driving.
  2. They add no visibility benefit beyond dipped headlights. Dipped headlights illuminate the road ahead, activate your rear lights and make you visible to following traffic. The RSA instruction for reduced visibility is to use dipped headlights — not hazard lights. If your dipped headlights are on, your rear lights are already on and you are already as visible as the regulations require.
  3. They create a false sense of safety. Drivers using hazard lights in rain often believe they are taking a safety measure. This can lead to maintaining speed in conditions where it is genuinely appropriate to slow down. Reduced speed in heavy rain is the safety measure — not flashing amber lights.

The correct actions in heavy rain: switch on dipped headlights, increase your following distance significantly (the two-second rule becomes a four-second rule minimum in heavy rain on Irish roads), and reduce speed to an appropriate level for the visibility available.

Hazards and Illegal Parking

A deeply ingrained habit on Irish roads is the belief that hazard lights suspended over a set of double yellow lines or a no-stopping zone create a temporary legal parking space. They do not.

Hazard lights do not create any parking exemption in Irish law.
The Road Traffic Acts do not provide any provision that hazard light use exempts a vehicle from parking restrictions. An Garda Síochána and local authority traffic wardens are fully entitled to — and regularly do — issue fixed charge notices to vehicles parked illegally regardless of whether their hazard lights are on. The vehicle is still in breach of the restriction and the fine stands.

Beyond the legal issue, a car stopped illegally with hazards on creates a real hazard for other road users: cyclists who must swing out into traffic, delivery vehicles forced to double-park, pedestrians whose crossing visibility is blocked, and bus passengers whose stop is obstructed. The hazard lights signal that the driver is aware they are causing a problem — which makes the choice to cause it more difficult to defend.

Hazards Disable Your Indicators — Why This Matters

This is the most practically important technical point about hazard lights and the one most drivers do not fully appreciate.

On most Irish cars, when hazard warning lights are active, the direction indicator system is either disabled or masked — a following driver cannot distinguish whether you have activated a left or right turn signal while hazards are flashing because all four indicators are already on together. On some modern vehicles the indicator may physically override the hazard on one side when you press the stalk — but this is not universal across all manufacturers and cannot be relied upon.

The practical consequence:
If you are driving on a dual carriageway in rain with hazards on and you need to change lane or exit at a junction, following drivers receive no warning of your intended direction. You simply move without any visible indication. This is a real cause of collisions — not a theoretical risk. Always cancel hazard lights before signalling and making any turn or lane change.

Hazard Lights on the RSA Driving Test

Hazard warning lights appear on the RSA driving test in two distinct contexts — as a secondary control check and as an observed behaviour during the drive itself.

RSA driving test — hazard light assessment:
  • Secondary controls check — at the start of the test, the examiner may ask you to demonstrate the hazard light button. You must locate and press it without hesitation, confirming all four indicators flash simultaneously. Know the button location in your specific test car before test day.
  • During the drive — if you use hazard lights incorrectly during the test drive (for example, switching them on while stopped at a traffic light or in heavy rain), this would be noted as a fault. Using them at the wrong time shows a misunderstanding of the control's purpose.
  • When required — if the examiner asks you to pull over for any reason during the test, switching on hazard lights when stopped in an unusual position is appropriate and expected.
Vehicle controls — tested from lesson one

BP Driving School covers every secondary control — including hazard lights — exactly as the RSA driving test requires. RSA-approved, Swords, North Dublin.

How to Operate Hazard Lights

The hazard light control is standardised across almost all modern cars sold in Ireland, though its physical location varies by manufacturer and model.

How to find and operate the hazard light button:
  • Symbol: a red triangle (outline of a hazard warning sign) — this is the internationally standardised symbol for the hazard light button
  • Location: typically on the centre of the dashboard, centre console, or top of the steering column. In older cars it may be a pull-out knob. In most modern cars it is a large, easily found button — often with the red triangle symbol illuminated
  • Operation: press once to activate — all four indicators flash simultaneously. The dashboard will show both left and right indicator arrows flashing at the same time. Press once again to cancel.
  • Works without ignition: on most cars, hazard lights work with the ignition off and the key removed — this is by design so a broken-down car can still warn other traffic even if the engine is not running
  • Test before your driving test: sit in your test car the day before and confirm you can locate and press the hazard button immediately without hesitation or searching

The Most Common Misuses in Ireland — and Why They Persist

Every one of these misuses is seen on Irish roads every day. Most persist not because drivers are careless but because they were never taught the correct rule, or because they learned from experienced drivers who were themselves doing it wrong.

Rain on the motorway

Ireland's climate means heavy rain on motorways is routine. The hazard-in-rain habit appears to have spread through imitation — a driver sees others doing it and assumes it is correct. It is not. Dipped headlights do the job correctly.

Stopped at school gates

Parents doing school pick-up or drop-off routinely use hazards to signal their stopped position. In practice, the school gate is an expected location — every approaching driver knows to expect stopped vehicles. Hazards add nothing and create confusion when the car is about to move.

Double-parked delivery vehicles

Commercial vans double-parked for deliveries with hazards on is a familiar sight on Irish town centre streets. The hazards do not prevent obstruction and do not provide legal parking. They do serve as a mild warning to approaching drivers — but the appropriate action is not to stop at all if safe alternatives exist.

Funeral cortège / following a hearse

Some Irish funeral corteges use hazard lights on all following vehicles to indicate the procession. This is an understandable use — indicating to other traffic that a convoy is in progress — and is generally tolerated. However, it is not a formally specified correct use under the lighting regulations.

The "thank you" flash

The double-flash of hazards as a courtesy gesture is a peculiarly Irish driving habit. In normal traffic it usually works as intended — but in ambiguous situations (approaching a junction, in a queue) it can cause confusion and occasionally alarm. A raised hand is clearer and does not involve the car's safety systems.

Driving through fog

Similar to rain — hazard lights while driving in fog are incorrect. Rear fog lights (the dedicated single red fog lamp) are the correct light to use in fog. Combined with dipped headlights, this provides the correct visibility in foggy conditions. Hazard lights while moving in fog prevent signalling and create confusion.

Frequently Asked Questions

Use hazard lights when your vehicle is stationary and poses a risk to other road users — after a breakdown, after an accident, or when stopped on a motorway hard shoulder. The one permitted use while moving is on a motorway or dual carriageway to briefly warn following drivers of a sudden unexpected queue or danger ahead. All other uses while moving — rain, junctions, slow driving — are incorrect.

No. Using hazard lights while driving in rain is incorrect and potentially dangerous. They disable your direction indicators — following drivers cannot tell which way you intend to turn. They provide no visibility benefit beyond properly used dipped headlights, which should always be on in rain. The correct action in heavy rain is dipped headlights, increased following distance and reduced speed.

Yes. The examiner may ask you to demonstrate hazard lights as part of the secondary controls check at the start of the test. You must locate and activate them immediately without hesitation. Incorrect use of hazard lights during the test drive — such as switching them on at traffic lights or in rain — would also be noted as a fault.

Yes, but only in a specific context — to briefly warn following drivers of a sudden queue or danger ahead on a motorway or dual carriageway. This should be a brief warning flash, not sustained use. Cancel the hazards as soon as following drivers have been warned and you are decelerating. Do not use them throughout normal motorway driving in rain or reduced visibility.

Stopping at a red light or junction does not make your car a hazard — every driver expects vehicles to be stopped there. Using hazards at a junction prevents you from signalling your intended direction when you move off, creates confusion for following drivers, and may confuse pedestrians about whether the car is about to move. Simply stop normally and wait.

No. Hazard lights provide no legal parking exemption under Irish law. An Garda Síochána and local authority traffic wardens issue fixed charge notices to vehicles parked illegally regardless of whether hazard lights are on. The vehicle is still in breach of the parking restriction and fully liable for the penalty.

The hazard light button displays a red triangle symbol and is typically located on the centre of the dashboard or centre console. Press once to activate all four indicators simultaneously — both dashboard arrow symbols will flash at the same time. Press once again to cancel. On most cars, hazard lights work without the ignition on, allowing them to warn other traffic even when the car is not running.

On most cars, direction indicators are disabled while hazard lights are active — a following driver cannot distinguish a left or right turn signal from the hazard flashing. On some modern vehicles the indicator may partially override the hazard, but this varies by manufacturer and cannot be relied upon. Always cancel hazard lights before signalling any turn or lane change.
Driving Emergencies & Breakdowns — Complete Series
Secondary controls — covered from your very first driving lesson.
BP Driving School walks every learner driver through hazard lights, dipped headlights, rear fog lights, front and rear demisters, wipers and washers in the format the RSA examiner requires — from EDT Session 1. Book your EDT course in Swords and North Dublin.

Also see the complete Pre-Drive Questions on the RSA Test guide — the secondary controls section covers every vehicle control the examiner may ask you to demonstrate on test day.