What are fog lights and when should you use them?

In the dark about fog lights? Allow us to shed some light on the subject

Fog lights are designed to aid visibility in, well, fog. The name may give the game away, but there is still some confusion surrounding when and how they should be used.

Aside from fog, fog lights are there to aid the driver in a number of low visibility condition where the standard head and taillights may be less effective. In this article we cover everything you need to know about fog lights, from when and how to use them, to the laws regulating their usage and placement.

Fog Light checklist

• At least one rear fog light must be fitted by law
• Front fog lights are optional
• Fog lights must only be used in adverse visibility
• You must not use fog lights when the weather is clear

What do fog lights do?

Fog lights are designed to aid visibility when bad weather conditions reduce your ability to see the road ahead. Front fog lights can cut through mist, fog, rain or even dust as they are mounted lower down than headlights in the front of the car.

Rear fog lights use very bright bulbs to cut through mist and fog to alert other road users of your presence.

Where are the fog lights on a car?

Front fog lights tend to be mounted low down, below the headlights. They illuminate the road directly in front of the vehicle. It is not a legal requirement to have front fog lights, and many manufacturers don’t offer them on their base models, reserving them for higher trims.

Rear fog lights are integrated into the rear light cluster and shine directly rearwards, their job being to alert the vehicle behind you to your presence when visibility is poor. Having at least one rear fog lamp is a legal requirement in the UK, and it must be fitted to the centre or offside rear of a vehicle.

Daytime running lights (DRL) have been a legal requirement in the UK since 2011, however, these are not the same as fog lights and do not aid visibility in inclement weather conditions. They are always on and are meant to make your car more visible rather than provide extra illumination.

When to use fog lights

Fog lights are useful when your visibility is decreased such as when it snows or there is thick fog or mist covering the road ahead. They can also help when there is heavy spray on the motorway.

Using your high beams in these conditions can actually reduce your visibility as the bright light reflects off the fog or mist, making it even harder to see ahead.

The highway code states that you must not use front or rear fog lights unless visibility is seriously reduced. Using this terminology means that this is a requirement and not a recommendation.

This is because incorrect use of fog lights can dazzle or blind road users, while rear fog lights can obscure your brake lights. The general rule is that you should only use them when you cannot see more than 100 metres ahead, this also applies to headlights. The highway code also states that you must switch both front and rear fog lights off when visibility improves.

You don’t always need to switch on both front and rear fog lights, the front ones should never be used to light the road in normal driving conditions, that’s what your headlights are for. Use your common sense, if it’s foggy but you can still see the road ahead, then there’s no need to have them on.

Rear fog lights should always be switched on whenever visibility is poor, they are there to alert other road users of your presence, not just to give you a clearer view of what’s behind you.

How do I turn my fog lights on?

Depending on the make and model of your car, there are a number of ways to turn on your fog lights. There will either be a separate button on the dashboard or a function on your indicator stalk which will allow you to control the fog lights.

Some cars have a rotary knob on the dashboard which can be pulled or pushed to activate the fog lights, others will have buttons next to this knob which will accomplish the same thing.

How do I know my fog lights are on?

Most vehicles will have a symbol that illuminates on the dashboard or driver display to show that the fog lights are on – just like with the head lights.
The symbol for the front fog lights (if fitted) is an oval-shaped lamp with three diagonal lines intersected with a wavy vertical line to the left of it.

The symbol for the rear fog lights is an oval-shaped lamp with three horizontal lines bisected by a wavy vertical line on its right.

When should I turn my fog lights off?

The Highway Code states drivers must switch the fog lights off when visibility improves. Leaving the front ones on may dazzle other drivers ahead, while the rear fog light (or lights) can obscure the brake lights. Neither the front nor rear fog lights may be left on when the vehicle is parked. You may get fined for incorrectly using your fog lights.

Do all cars have fog lights?

All cars must have at least one rear fog light as a legal requirement in the UK. They must be fitted to the centre or offside rear of a vehicle. Front fog lights are not required to be fitted, and most manufacturers reserve them for their more expensive models. You will generally see them mounted low down into the bumper, below the headlights.

You may notice a thin LED strip on the front of some cars, these are Daytime Running Lights (DRL) and have been fitted to all new cars in the UK since 2011. They turn on whenever the car is switched on and are there to make the car more visible to other road users. They do not perform the same function as front fog lights.

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