An amber or yellow symbol that looks like a headlight with wavy or diagonal lines pointing backwards has appeared on your dashboard. This is the rear fog light indicator. Unlike the green headlight indicators that are informational, this amber indicator has a specific message: a very bright red light at the back of your car is currently switched on. This guide explains exactly what that means, when you should have it on, and why leaving it on unnecessarily is one of the most common and irritating things a driver can do to everyone behind them.
What Does the Rear Fog Light Indicator Look Like
The rear fog light indicator is usually amber or yellow and shows a headlight or beam symbol with lines that point toward the rear of the car, often shown as diagonal or wavy lines going in the opposite direction to the front fog light symbol. Some cars use a symbol that looks like a reversed version of the front fog light indicator.
On many dashboards, the rear fog light symbol faces left or has backwards-pointing lines to distinguish it from the front fog light symbol, which faces right or has forward-pointing lines. The colour is almost always amber, distinguishing it clearly from the green headlight indicators.
What Is the Rear Fog Light
The rear fog light is a single very bright red light mounted at the rear of the car, separate from the standard taillights. It is significantly brighter than the normal taillights, often described as similar in brightness to a brake light but on constantly rather than flashing.
Its purpose is to make the car visible from behind in conditions of very low visibility, specifically in dense fog, heavy snow, or very heavy rain where the standard taillights may not be bright enough to be seen by following drivers at a safe distance.
Most cars have a single rear fog light, though some have two. It is activated by a separate switch or button from the main headlight controls, usually requiring the headlights to be on before the rear fog light can be activated.
When You Should Use the Rear Fog Light
The rear fog light should only be used when visibility is severely reduced, generally accepted as when you cannot see further than 100 metres ahead. In practice, this means:
Dense Fog: When driving in fog thick enough that following drivers genuinely cannot see your standard taillights at a safe braking distance, the rear fog light significantly increases your visibility. This is the primary use case the rear fog light was designed for.
Very Heavy Snow: When snowfall is heavy enough to reduce visibility severely, the rear fog light serves the same purpose as in fog. Light or moderate snowfall does not qualify.
Extremely Heavy Rain: In conditions of torrential rain where spray and reduced visibility make standard taillights difficult to see, the rear fog light can be appropriate. Normal heavy rain does not qualify.
The key test is always visibility distance. If you can see the tail lights of the car in front clearly at a reasonable distance, the rear fog light is not needed.
When You Should Not Use the Rear Fog Light
This is the section that matters most for everyday driving, because the rear fog light is one of the most commonly misused features on any car.
Normal Rain or Drizzle: Activating the rear fog light in light or moderate rain is one of the most frequent misuses. Standard taillights are perfectly visible in normal rain. The rear fog light in these conditions is not needed and actively dazzles the driver behind you.
Clear Conditions After Fog Has Cleared: Many drivers switch on the rear fog light when entering fog and then forget to turn it off once conditions improve. Driving on a clear motorway with the rear fog light still on is a very common sight and causes significant glare for following drivers, particularly at night.
Night Driving Without Fog: The rear fog light is not a night driving aid. It is not designed to improve visibility at night in clear conditions. Switching it on simply because it is dark and you want to be more visible creates unnecessary dazzle for other drivers.
Slow Moving Traffic Using the rear fog light in slow-moving traffic is particularly disruptive because following drivers are much closer than on a free-flowing road. At close range, the rear fog light at that brightness makes it very difficult for the driver behind to distinguish between the fog light being on constantly and the brake lights activating. This delays brake light recognition and actually reduces safety.
Why Leaving the Rear Fog Light On Is a Problem
The rear fog light is extremely bright by design. When conditions do not warrant its use, it creates two specific problems for the driver behind.
The first is glare. A rear fog light in clear conditions causes significant eye strain for the following driver, particularly at night. It is bright enough that it can temporarily affect vision when looking away from it.
The second is brake light confusion. Because the rear fog light is similar in colour and brightness to a brake light, drivers behind find it harder to notice when the brake lights actually come on. The brake light signal becomes harder to distinguish against the already-bright fog light. This reduces reaction time in a braking situation.
In many countries, using a rear fog light in conditions that do not warrant it is an offence under road traffic regulations.
How To Turn Off the Rear Fog Light
The rear fog light has its own dedicated switch or button, separate from the main headlight controls. On most cars, it is a pull or push switch on the headlight stalk, or a button on the dashboard near the headlight controls. The amber indicator on the dashboard confirms when it is on.
To turn it off, press or pull the rear fog light control back to its off position. The amber indicator on the dashboard should go off, confirming the rear fog light has deactivated.
If you are unsure where the rear fog light control is on your specific car, check the car manual. It will show the exact control location and the symbol used on your dashboard.
Front Fog Lights vs Rear Fog Light
Many drivers confuse the front fog light indicator with the rear fog light indicator. Here is the clear difference.
The front fog light indicator is usually green and shows lines pointing forward. Front fog lights are lower-mounted lights at the front of the car designed to illuminate the road surface in fog without the light bouncing back off the fog itself. They help the driver see the road close ahead in low visibility.
The rear fog light indicator is amber and shows lines pointing backwards. The rear fog light is at the back of the car and is purely for making the car visible to following drivers, not for illuminating anything for the driver.
Some cars have both front fog lights and a rear fog light. Others have only the rear fog light. Check your car manual to know which your car has.
Rear Fog Light Left On After MOT or Service
A common reason drivers notice the rear fog light indicator unexpectedly is after the car has been in a garage for an MOT, service, or repair. Mechanics routinely check all lights during a vehicle inspection and sometimes leave the rear fog light on when returning the car. If you notice the amber indicator after collecting the car from a garage, this is the most likely reason.
Quick Summary
|
What |
Detail |
|
Indicator Color |
Amber or Yellow |
|
Symbol |
Headlight with backwards-pointing lines |
|
When To Use |
Dense fog, very heavy snow, torrential rain reducing visibility below 100 metres |
|
When Not To Use |
Normal rain, clear night driving, slow traffic, after fog has cleared |
|
Key Risk |
Dazzles following drivers, masks brake light signals, may be a legal offence |
|
How To Turn Off |
Rear fog light switch or button, separate from main headlight controls |
Related Indicators and Lights
These indicators are all part of the lighting and visibility system:
- Low Beam Indicator – Green indicator for standard dipped headlights
- High Beam Indicator – Blue indicator for full beam headlights
- Daytime Running Lights Indicator – DRL system and the dusk rear visibility risk
- Hazard Lights Indicator – Incorrect use of hazard lights in poor visibility
This page is part of our complete guide to car dashboard symbols and meanings. To see every warning light explained in one place, visit our Car Dashboard Symbols.