Is it illegal to drive with steamed up windows?

DRIVING with steamed-up windows can not only be dangerous but also illegal, as it impairs visibility and increases the risk of accidents.

It is important to understand the best methods to ensure clear and safe driving conditions.

Is it illegal to drive with steamed up windows?

Yes, it is illegal to drive with steamed-up windows if it impairs your ability to see clearly.

In the UK, driving with obstructed visibility due to fogged-up or misted windows can be considered dangerous and result in penalties.
      
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".

Failing to clear your windows properly can result in a fixed penalty fine of up to £2,500 and three penalty points on your license.

Additionally, if the offence is committed within three years of a previous conviction for the same issue, it could lead to disqualification from driving.

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?

Your car windscreen can steam up for several reasons, primarily related to moisture and temperature differences.

When the inside of your car is warmer than the outside, the warm, moist air inside condenses on the colder windscreen.

This is particularly common during colder weather or when the car has been parked outside in the cold.

Increased humidity inside the car, due to passengers' breath, wet clothing, or spills, can also contribute to condensation on the windscreen.

Additionally, high humidity or rain can introduce extra moisture into the car, especially if windows or doors are left open.

If your air conditioning or heating system is not functioning properly, it might not adequately control humidity or temperature, leading to more condensation.

To reduce fogging, it’s important to maintain a balance between the temperature inside and outside your car, use your vehicle’s defroster and air conditioning systems effectively, and keep the interior of your car clean and dry.