Is it illegal to drive with steamed up windows?

MOST drivers are familiar with the frustration of having a steamed window – whether it’s first thing in the morning or a change in conditions while driving.

Both old and new cars are susceptible to it – but is it illegal to drive with a steamed up window.

It is against the law to drive with a steamed up window


It is against the law to drive with a steamed up windowCredit: Getty

Is it illegal to drive with steamed up windows?

As well as being extremely dangerous, driving with a misted window is an offence.
The Road Vehicles Lighting Regulations 1989 regulations 23 & 27 and the Highway Code states that ‘windscreens and windows MUST be kept clean and free from  obstructions to vision’.

If you fail to clear windows properly, it can lead to a fixed penalty fine of up to £2,500, three penalty points or even disqualification if the offence is committed within three years of a previous conviction for the same offence.

This may seem unfair because no one can control the weather, so why should you be liable when weather is a factor in an accident?

The reality is that motorists have the power to choose whether or not to drive in hazardous conditions and change their driving behaviours to help combat the effects. 

How can I clear my windscreen?

Use the heater

Start the heater off cold, then slowly increase the temperature as the air dries out, rather than overloading the cabin with hot, ‘wet’ air.

Try to find a temperature and humidity that’s comfortable but doesn’t mist up the cabin.

Make sure your heater’s blast is directed at the windscreen and the windows – the warmer air (even on cold the air will be warmer than the ice cold windscreen) will dry the glass a little through evaporation and begin to heat up the glass to stop the water vapour condensing on it again.

Use the air-con

If your car has air conditioning make sure it is switched on and is used in conjunction with the heater.

Hot air will dry the glass a little through evaporation, but the air will then cool down and condense on the glass once more, so make sure the air-con is on to keep the atmosphere inside dry.

Use your windows

If you don’t have a clever climate control system, having the windows down could actually help clear the screen faster.

This helps because the dry, cold air from outside can help reduce the amount of water vapour inside the car, stopping the screen misting up.

Climate control system

If you do have a clever climate control system, utilise it. There’ll most likely be a setting for demisting the windscreen, which will automatically adjust the ventilation system’s parameters to achieve the best results. 

Why does my car windscreen steam up?

Car windows fog up when warm moist air comes into contact with the cold glass surface.

The heat from your body and breath warms the air inside the car and increases the moisture levels.

When the moist, warm air then comes into contact with the cold glass, it condenses and causes the mist or fog on the windscreen and windows.

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