Drivers are being warned of travelling in fog this week with cool air mixing with warm moist air, as Britain braces itself for a heatwave.
Experts advise motorists to use fog lights when they cannot see for more than 100 metres In front of them, but must switch them off when the fog has cleared.
Rules 234 to 236 of the Highway Code urge drivers to be careful when driving on a road or motorway if it is foggy and visibility is reduced.
Drivers must also abide by any “fog” signs on gantries above the road as even if it seems to be clearing, motorists can suddenly find themselves in thick fog.
The Highway Code deals with how to properly drive in fog
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Motorists should use their lights as required, keep a safe distance behind the vehicle in front and be able to pull up well within the distance they can see clearly.
When in a patch of thick fog, drivers should check their mirrors before they slow down and then use their brakes so vehicles behind will be warned by the brake lights that they are slowing down.
Rule 236 states that drivers must switch off their front or rear fog lights when visibility improves.
It adds: “You MUST NOT use front or rear fog lights unless visibility is seriously reduced as they dazzle other road users and can obscure your brake lights.”
According to the RAC, drivers are at risk of being fined if they do not use their fog lights properly when they are needed.
The Road Vehicles Lighting Regulations 1989 prohibits the use of front and rear fog lights to dazzle other drivers when visibility is not reduced or when the vehicle is parked.
This means that fog lights when it is drizzling or raining is also not allowed, with drivers being eligible to receive a fine from the police, usually between £30 and £50.
Drivers can find the fog light button on their dashboard, on their steering wheel or on their indicators.
The front fog light symbol shows a lamp with slanting lines of light in front of it pointing left, with the lines being intersected by a wavy line.
The rear fog light is the same as the front symbol but in reverse, with the light and fog lines appearing after the bulb, pointing right.
A spokesperson for the AA said: “Remember that when it’s foggy, it can be harder to tell if other vehicles are moving.
“Many accidents happen because drivers don’t realise that the car in front of them has stopped. That’s why it’s safer to slow down and leave a bigger stopping distance.
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Drivers could receive a fine of between £30 and £50
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“If it’s foggy or misty, the roads might also be wet, which means it could take longer to stop.”