When to Use Fog Lights in Ireland (Front and Rear)
Short answer: in Ireland, use fog lights only in dense fog or falling snow, when you can’t see more than about 100 metres ahead, which is roughly 25 car lengths. Always use your dipped headlights as well, and switch the fog lights off as soon as visibility improves. Fog lights aren’t for ordinary rain, darkness or mist where you can still see well.
The Road Safety Authority (RSA) has found that many drivers use fog lights when they don’t need them. Here’s what front and rear fog lights are for, when to turn them on and off, and the mistakes to avoid.
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Front and rear fog lights: what’s the difference?
They do two different jobs.
- Front fog lights sit low on the front bumper. They help you see, by lighting up the road surface and edges underneath the fog with a wide, low beam.
- Rear fog lights are bright red lights at the back of the car. They help other drivers see you, and they’re far brighter than your normal tail lights.
Not every car has front fog lights, but most modern cars have a rear fog light. If you’re not sure what yours has, check your owner’s manual or the switch on the dashboard.
The 100 metre rule
The RSA advises that you can only use fog lights in dense fog or falling snow, if you can’t see more than 100 metres, about 25 car lengths. That’s roughly the length of a football pitch. If you can see further than that, you don’t need them.
A quick way to judge it: on a road with roadside posts, or with the lights of the car ahead, check whether you can still clearly see something about a football pitch away. If you can, keep the fog lights off. You can read more in TheJournal.ie’s report on the RSA advice.
When to use fog lights and when not to
| Conditions | Fog lights? | What to use |
|---|---|---|
| Dense fog, you can’t see beyond about 100 m | Yes | Dipped headlights, plus front and rear fog lights |
| Falling snow, you can’t see beyond about 100 m | Yes | Dipped headlights, plus front and rear fog lights |
| Light mist, you can see well ahead | No | Dipped headlights |
| Heavy rain, but visibility is good | No | Dipped headlights |
| Night driving on a clear night | No | Dipped headlights, and full beam where it’s safe |
| Fog has cleared | No | Switch fog lights off |
How to use fog lights properly
- Switch on your dipped headlights first. Fog lights are an addition, not a replacement.
- Add your front fog lights if you have them, and you can’t see more than about 100 metres.
- Add the rear fog light so drivers behind can see you. Look for the symbol on the dashboard so you know it’s on.
- Slow down. The RSA advises reducing your speed in fog, and making sure you can always stop within the distance you can see.
- Leave a much bigger gap to the car in front.
- Switch fog lights off as soon as visibility improves.
Don’t use full beam in fog. The light reflects back off the water droplets, which creates glare and makes it harder to see.
Common fog light mistakes
- Using them in rain or at night. Fog lights are for dense fog and falling snow, not for ordinary bad weather.
- Leaving the rear fog light on. In clear conditions it dazzles the driver behind and can hide your brake lights.
- Forgetting they’re on. Some cars don’t make it obvious. Check the dashboard symbol when the fog clears.
- Using them for looks. Fog lights that are on all the time can dazzle other drivers.
Are your fog lights working?
You don’t want to find out that a fog light is dead when the fog is already down. Check them now: switch on the dipped headlights, then the fog lights, and walk around the car or reverse up to a reflective surface. If a rear fog light isn’t working, our guide on rear fog light not working shows how to find the fault. If a unit is damaged, you can browse used fog lights on Autolight.
Wondering whether your car switches them on for you? See auto fog lights explained.
Fog light FAQs
When can I use fog lights in Ireland?
Only in dense fog or falling snow, when you can’t see more than about 100 metres. Switch them off as soon as visibility improves.
Can I use fog lights in rain?
Not in ordinary rain. Use your dipped headlights. Fog lights are for dense fog and falling snow.
Do I use fog lights with dipped headlights?
Yes. Dipped headlights are your main lights in low visibility, and fog lights are added on top when the fog is dense.
Should I use my rear fog light in fog?
Yes, when visibility is seriously reduced, so drivers behind can see you. Turn it off as soon as it clears, because it can dazzle them and hide your brake lights.
How do I know my fog lights are on?
A symbol lights up on the dashboard when they’re on. Check your owner’s manual for the symbol on your car.
Need a replacement fog light?
Browse used car fog lights in Ireland and filter by make, model, year, side and county.
