- How to drive in fog
- What is fog?
- What should you do when driving in fog?
Driving in foggy conditions can be really eery. Especially if you’re caught on an unfamiliar Country road or seemingly deserted high street. I’ve often found myself caught in a patch of thick fog. Because I’m a self-confessed horror film addict and I’ve watched too many in my time. I find myself imagining a cluster of zombies in the distance. Anyone else or just me? Anyway, driving in fog is not only eery but it can be dangerous. If you’ve ever been driving through the thick fog you’ll know it is almost impossible to see even a few feet in front of the car. This can be really unnerving and you should always drive cautiously through the fog. In this article, we’ll take you through our top tips for driving in fog.
What is fog?
Did you know there are different types of fog? Yes, you heard me right, different types of fog depending on your location and the composition of the fog. Knowing your fog types may only seem like useless unless you’re a whizz at the pub quiz. But it can help you to safely respond to the situation when driving.
Below are the most common types of fog and the ones which pose the most threat to you as a driver. If you want to know more about types of fog the Met Office have some great information.
Freezing fog is a compound of highly cooled water droplets which manage to remain liquid despite external temperatures reaching below freezing. This type of fog poses a threat to drivers because ice gets deposited on your windscreen. The situation can be exacerbated if you decide to clear your windscreen with screen wash which will add a freezing level of sheet ice further limiting your visibility.
This is a localised area of fog that occurs when cold air moves over warm water. It usually occurs in autumnal climates when water temperatures are still warm from summer but the air is already starting to cool. Evaporation fog doesn’t pose a great threat to drivers as it’s usually not across the roads, but on the odd occasion, you find yourself in a patch of evaporation fog you will usually pass it quite quickly.
Valley fog forms when cold dense air settles in the lower parts of a valley and condenses to form fog. This comes with a temperature change as warmer air passes above the cold air to form fog. Valley fog usually occurs during winter and can last for several days if conditions are calm.
How to drive in fog
Firstly, if you’re watching the weather forecast and notice that fog has been forecast or a weather warning has been issued then you really should only drive if absolutely necessary. Minimise your risk of being involved in an accident by not putting yourself in a potentially hazardous situation. If you do need to drive then the following tips for driving in fog will help you stay safe.
Check your headlights
You should check your headlights regularly to ensure they are working properly. But let’s be honest, we don’t always remember to do this. If you’re starting a journey knowing you may encounter fog then it’s worthwhile checking your lights before you set off. Turn on your dipped beams and check the lights are working on both sides, at the front and at the back of the car.
If it starts to get foggy, even in daylight, you should turn on your headlights. This will ensure you are visible to other road users from the rear. It usually won’t improve your own visibility a great deal, but it will certainly help others to see you which is just as important. You should make sure your headlamps are set to the dipped beam setting if you want to improve your own visibility.
A lot of drivers assume that in foggy weather they should use the brightest beam they can. Increased light equals increased visibility, right? In the case of fog, this is the wrong thing to do and will actually reduce your visibility. The fog acts as a reflective screen and throws the beam light back at you.
It is a legal requirement that all cars are fitted with rear fog lamps. Many drivers switch these on as soon as they encounter a tiny patch of fog. This is dangerous as the lights are designed to shine through very heavy and thick fog. If the fog isn’t heavy enough then you will potentially ‘blind’ other road users as you turn your car into a beacon of distracting light. Fog lamps should only be used in cases of heavy fog. The Highway Code says that you should only use your fog lamps when the visibility drops below 100m.
They will only work if you switch them on and if the headlamps are on. If you don’t know where your fog light switch is then it’s a very good idea to check next time you get in your car. The last thing you need when the fog starts to get thicker is to be scrabbling around for the switch.
Some modern vehicles are also fitted with front fog lamps. These are designed to help you see the edges of the road and improve your visibility a little bit in a very heavy fog. The difference they make is only small, but if you do use them the same rules apply that they shouldn’t be used unless absolutely necessary.
When the fog clears you must remember to turn off your fog lights as soon as possible. If you keep them on then you will be dazzling other road users. In patchy fog, you are expected to turn your fog lights on and off as you pass through patches of fog and clear road.
Use your in-car heater
Fog can cause condensation internally on your windscreen. This can happen without you noticing in foggy conditions so ensuring you’ve switched on your heater during foggy weather is best practice. Most modern cars are equipped with good heaters so ensuring you are familiar with how to clear your windscreen using the de-misting function will help you ensure you don’t have condensation to further reduce your visibility.
When one of your senses is removed or reduced then you must rely on your others to get by. In the case of thick fog, your sight will be reduced and you’ll need to use your ears to listen for oncoming cars. Turn off your music and wind your window down at roundabouts and junctions to ensure you can hear any oncoming vehicles. When driving on motorways it is useful to be able to hear overtaking vehicles you might not be able to see.
Keep your distance
In any situation that poses a higher risk of accident, you should always keep a safe distance from the car in front. This should be at least two car lengths between you and the car in front.
Finally, the most obvious and natural safety measure when driving in fog is to reduce your speed. Some drivers find they go faster in fog as the usual markers of road speed perception are hidden. Of course, this is dangerous, especially if there are cars without their lights on ahead of you and out of view or parked cars which can come out of nowhere if you’re speeding through the fog.
What should you do when driving in fog?
There are ten key tips you should be aware of if you are driving in fog, or know that you are likely to encounter it on your journey (because it’s been forecast).
- Check your mirrors and slow down before entering any fog.
- As we’ve previously mentioned, you should maintain a greater distance between you and the vehicle in front of you. If your visibility has been affected, then the chances are theirs is too. It’s recommended that you should increase the gap from two seconds to four.
- Use your lights if visibility has been reduced to less than the size of a football pitch (100 metres).
- Knowing the location of your fog light switch is vital, so before you set off on a journey make sure you know where it is.
- Don’t use the tail lights of the car in front of you as a form of navigation, this offers you a false sense of security. Remember that their visibility will be as poor as yours.
- When reaching junctions and crossroads open your window so that you can listen out for other traffic if your visibility has been reduced by fog.
- Don’t switch your lights on full-beam, fog causes light to reflect back to you and this can reduce your visibility even further than it already has been.
- Use your wipers and keep your windscreen de-misted – using your car heating can aid with this.
- If a road signal is showing ‘fog’ but the road ahead seems clear, be prepared to drive into a bank of fog or some patchy fog.
- If visibility is truly that bad, stop until it is safe for you to continue your journey.
Driving in fog can be dangerous so it’s important that as well as considering your own visibility it’s important to think about the visibility of other drivers on the road. Ensure that you make yourself as visible as possible and keep your distance. We hope these tips will help you stay safe during the fog.