Fog happens when a thick cloud of tiny water droplets is suspended at or near the Earth’s surface. Dense fogs are sometimes known to occur in industrial areas, where there are many pollution particles that water droplets can attach to. Travelling in fog can be extremely dangerous because of decreased visibility. Fog can drift rapidly and is often patchy. Warnings of dense fog are issued when visibility is expected to fall below 200 metres. Severe disruption to transport occurs when visibility falls below 50 metres.
Met Office Dense Fog Warnings
The United Kingdom’s National Weather Service, the Met Office, provides up-to-date weather advisories and warns the public of severe or hazardous weather through its National Severe Weather Warning Service. Warnings are given a colour (Green, Yellow, Amber or Red) based on the combination of both the likelihood of the severe weather event occurring and the impact the weather conditions may have. Make sure you check your local weather forecast to find out whether the Met Office has released any warnings for your area. You can also find the latest warnings at www.metoffice.gov.uk
The Met Office provides the following examples of what to expect during dense fog.
Very Low Threat (Green)
Low Threat (Yellow)
Medium Threat (Amber)
High Threat (Red)
If the Met Office issues a warning for dense fog in your location, make sure you are prepared. Use the following tips and hints to help ensure your safety.
What to Do When Travelling in Dense Fog
- Avoid travel if possible.
- Drive very slowly with dipped headlights, as full-beam lights reflect off the fog, which causes a 'white wall' effect.
- Keep an eye on your speed—fog can give the illusion of moving in slow motion.
- Use fog lights, but remember to turn them off when visibility improves.
- Don't hang on the tail lights of the car in front; rear lights can give a false sense of security. Use a ‘twosecond rule’ to leave enough space between you and the car in front.
- If visibility is extremely limited, wind down windows at junctions so you can hear approaching traffic.
- Watch out for freezing fog, which is made of water droplets that freeze on contact with objects such as the road and the car. It can quickly form a layer of ice.
- The safest option when you’re on the road is to pull over and stop until it is safe to continue.
Stay safe when severe weather strikes by being prepared and checking weather forecasts and warnings.