Fog

Fog is one of the most dangerous weather conditions. An incident involving one vehicle can quickly involve many others, especially if they’re driving too close to one another.

Motorway pile-ups in fog have sometimes involved dozens of vehicles. All too often there’s a loss of life or serious injury that could easily have been prevented.

Observe the obvious

If it’s foggy and you can only see a short distance ahead, you should start thinking about how the conditions will affect your driving.

Do you need to drive?

Take alternative transport or postpone your journey, if at all possible. If you must drive, give yourself time to prepare.

Check all the lights on your vehicle, clean your windscreen, and ensure you have made every effort to remain as visible to other road users as you possibly can. This should also include wiping your number plates. Remember that foggy conditions mean that your journey will take longer, so try to allow yourself more time and plan rest stops where appropriate.

Use of lights

Correctly adjusted fog lights can be a valuable aid when driving in fog.

In daylight

You MUST use your dipped headlights when visibility is seriously reduced.

• They’ll be seen from a much greater distance than sidelights.
• They won’t dazzle other drivers or pedestrians in the daytime.

You should also use dipped headlights, or at least sidelights, in relatively light fog. Remember that, even if you think you can see far enough ahead, your own vehicle might not be clearly visible to others until you’re too close. If in any doubt, always try to maximise your visibility in the interests of safety.

Use fog lights if your vehicle is fitted with them.

At dusk

Use dipped headlights at dusk and other times when visibility is poor.

At night

Slow down and use dipped headlights, not main beams. If you can’t see for more than 100 metres, switch on your front and rear fog lights, if fitted.

High-intensity rear fog lights

If your vehicle has high-intensity rear fog lights, use them in fog only when visibility is seriously reduced. Normally this means when you can’t see for more than 100 metres (328 feet).

Adjust your lights

Change your lighting with the conditions. For example, when you’re queuing in traffic and the driver behind has already seen you, it can be helpful to switch off your rear fog lights temporarily to avoid dazzling them.

Driving in fog

Poor visibility is frustrating and a strain on the eyes. Your ability to anticipate is dangerously restricted. It’s also much more difficult to judge distances and speed in fog when outlines become confusing. You can easily become disoriented – especially on an unfamiliar road.

In the interests of safety, you MUST

• slow down – check the speedometer from time to time
• be able to stop well within the distance you can see to be clear
• use your windscreen wipers to keep the outside of the screen clear • use your demister to keep the inside of the screen clear. Use your heated windscreen if your vehicle has one.

Do

• give yourself plenty of time and space to deal with whatever is ahead. Decide what’s a safe speed for the conditions and stick to it. Don’t let other drivers push you into driving faster
• watch out for emergency vehicles. There could well be an incident ahead.

Don’t

• follow the vehicle in front too closely
• try to keep up with the vehicle ahead. You’ll get a false impression that the fog isn’t too bad if you ‘hang on’ to the lights of the vehicle ahead because it will displace some of the fog
• use main beam when you’re in fog as the fog reflects the light and can dazzle you, reducing your visibility even further. It can also dazzle other drivers.

Fog patches

The density of fog varies. Sometimes the fog is patchy. One moment it can be fairly clear, the next extremely dense. Avoid the temptation to speed up between the patches.

Following another vehicle

Slow down and leave plenty of room for stopping. There may be something ahead which you can’t possibly see until you’re too close to it.

You must leave enough space to react and brake in case the vehicle in front has to stop suddenly.

You may not see or recognise that the vehicle ahead is braking or has stopped as soon as you would in clear weather.

Remember the road surface is often wet and slippery in fog; you need to be able to brake safely.

Overtaking

Overtaking in fog can be particularly dangerous. You could well find that visibility ahead is much worse than you thought, and you won’t be able to see oncoming traffic soon enough.

Dealing with junctions

Dealing with junctions in fog needs particular care, especially when turning right. You should

• open your window(s) and switch off your radio/CD player so you can hear any approaching traffic
• start indicating as early as you can
• make full use of your lights. Keep your foot on the brake pedal while you’re at a standstill – your brake lights will give drivers behind an extra warning. However, when another vehicle stops immediately behind you, take your foot off the brake pedal so you don’t dazzle the driver
• use the horn if you feel it will help, and listen for other vehicles.

Don’t turn or emerge until you’re absolutely sure it’s safe.

Road markings

Dipped headlights will pick out reflective road studs, but it’s not so easy to recognise other road markings when driving in fog. Explanations of the different coloured road studs are given in section 6.

Try to keep a central position between lane lines or road studs. Don’t mix up lane lines and centre lines. Driving too close to the centre could mean you’re dangerously near someone coming the other way who might be doing the same thing. Driving on the centre line as a means of finding your way is extremely dangerous.

On rural roads, there are black-and-white marker posts, with red reflectors on the left-hand side of the road and white reflectors on the right-hand side of the road. These mark the edge of the road and are especially useful at night or at other times when visibility is reduced.

Stopping

Parking

Never park on a road in the fog if you can avoid it. Find an off-street parking place. However, if it’s unavoidable, always leave your parking lights or sidelights on.

Don’t leave dipped headlights or the main beam on. In foggy conditions, these can lead other road users to wrongly think they’ve drifted over to the extreme right-hand side of the road. If they quickly try to correct this positioning in order to keep to what they think is the left-hand side, they’ll mount the pavement. This would be very dangerous for any pedestrians and other road users nearby. There might also be damage to walls, properties, street furniture and other vehicles. In rural areas there might be a ditch instead of a path, or even an embankment leading down to water.

Breaking down

If you break down, get your vehicle off the road if you possibly can. Inform the police, and make arrangements to remove it as soon as possible if it creates an obstruction. Never leave it without warning lights of some kind, or on the wrong side of the road.