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Fog Lights: What They Are, and How They Help You Drive in Fog

By Stephen Fogel, June 14, 2018

fog lamps

No matter how good you are behind the wheel, it’s tough to drive in fog. Your visibility is reduced — sometimes greatly — which means you have less time to react to other cars, critters darting into the road, and even simple curves.

Your headlights aren’t a great help in this situation. The water droplets that make up fog are extremely reflective. Your lights reflect off the fog, creating glare and further reducing your visibility. Using the high beams just makes it worse. 

This is where fog lights come in. While they don’t clear everything up, they’re on your car for a reason. Let’s learn how they work, go over how to drive in fog, and find out what to do if your fog lights stop working.

How fog lights are different

Fog lights are mounted low, often under the headlights. This takes advantage of the fact that the fog nearest to the ground is often much less dense, and easier to see through. These lamps are designed with a specialized light pattern. Unlike the broad, tall, long-range beam of your headlights, fog lights throw a wide but low bar-shaped beam of light onto the road directly ahead of your vehicle.

The unique design of your fog lights helps to illuminate the edges of the road and the lane markings so that you can see things better. It also reduces the amount of reflected glare from the fog itself. 

Fog lights can help you during rainy, dusty or snowy conditions, as well. Keep in mind that fog lights work best at lower speeds, when seeing the road immediately in front of your vehicle is most important.

How you turn on the fog lights depends on what kind of car you have. There’s often either a separate setting on the switch that controls your headlights or a button you can press to turn them on and off. Check your owner’s manual.

5 tips for driving in fog

While we’re talking about fog, let’s review some basic tips for driving in it.

1. Slow down. Limited visibility is dangerous. The thicker the fog, the slower you should go. Make sure not to tailgate the person in front of you.

2. Use your headlights and fog lights. But avoid the brights. They won’t help you see farther, and the reflection will only hurt your own vision. 

3. Use your windshield wipers and defroster. Fog means moisture, and moisture on your windshield will hurt your visibility even more. Use the wipers and defroster to keep the glass clear.

4. Use the lane markers as your guide. If the visibility is really bad, follow the painted stripe on your right . The one on your left can be helpful, but looking that way could mean staring at oncoming headlights, which would temporarily hurt your vision.

5. Don’t stop on the road. If the visibility is so bad that you can’t see at all, you’ll be tempted to stop. If you do this, you’ll want to pull as far off the road as you safely can and turn off all your lights. If a car behind you sees your tail lights or bumper, it might think you’re in a traveling lane and head right for you.

What are rear fog lights?

Many vehicles today come with rear fog lights. These are often found on cars from manufacturers based in Europe, where rear fog lights are required.

The purpose of rear fog lights is not to see, but to be seen. These intense red lights are meant to prevent people behind you from running into you. By making your vehicle more visible, rear fog lights provide an extra margin of safety under foggy conditions.

If you have these, remember to turn them off when the fog lifts. They are very bright and will limit the ability of drivers behind you to see clearly.

» LEARN MORE: Get an estimate for your fog light replacement

What to do if your fog lights stop working

With the exception of the LED fog lights on some newer vehicles, most use a conventional bulb that can burn out after a while. If you notice that one of your fog lights is out, looks dim or is flickering, it most likely means the bulb needs replacing. If you don’t feel comfortable tackling any aspect of this job, ask your mechanic for help.

First, check the fuse

If both fog lights go out at the same time, the problem could very well be a blown fuse for the fog light circuit. Check your owner’s manual for the location of the fuse box and the fog light fuse. 

With the ignition off, pull out the fuse and see if it has blown. If it looks OK, put it back in place. If it has blown — the thin metal part inside the fuse has broken or separated — then you will need to replace the fuse with one of the same rating. 

Now start your vehicle and try the fog lights. If they work, you’re done. If they blow out again or do not come on, see your mechanic. 

Replace the fog light bulb

Removing a burned-out fog light bulb and replacing it with a new one may be easy — but not always. It usually consists of removing the bulb, disconnecting it from its base, then reversing the process with the new bulb.  

But it all depends on how accessible your car’s fog lights are. Some cars give you easy access, while others may require you to reach deep under the hood or to disassemble the fog light housing to get to the bulb.

Check your owner’s manual for the correct bulb replacement procedure, then look at your vehicle to see if you can manage it. If you can take care of it, just remember to never touch a bulb with your bare fingers, as oils from your hand could cause the bulb to break when it heats up. Instead, use a clean dry cloth.

If the process looks too difficult, have your mechanic take care of it instead.

Get it diagnosed by a professional
 

The future of fog lights

New technologies may make fog lights obsolete in the near future. Sophisticated laser headlights, already in use in Europe, can adjust their light patterns for road, speed and weather conditions. Night-vision systems have already appeared on some luxury cars. 

These systems use infrared sensors to detect the heat signatures of various objects, displaying them on a screen in front of the driver. Current driver assistance technologies use radar to sense objects ahead, automatically braking to avoid crashes.

As they become more commonplace, self-driving vehicles will use lidar (laser-based radar) to completely map out their surroundings in any weather. They will also be in constant communication with all the other self-driving vehicles around them. These autonomous vehicles will be able to see and react to everything around them, long before a driver would be aware of any hazards. 


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