Wednesday 16th September 2015
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Car modification laws in the UK are regularly updated. Therefore, you should check these thoroughly before making any modifications to your own car. You could end up paying thousands of pounds for something that is illegal. This brings us to the topic of this blog: how legal are modified cars?

What isn’t legal:

Large or big bore exhausts are illegal to use on public roads, even if the vehicle passed its MOT. Big bore and sports exhaust systems are fitted to increase the sound but this actually contravenes the Type Approval of the car and is an offence. 

A police opinion that the system isn’t standard and is noisier than a non-modified vehicle of the same spec is enough to get you into trouble! 

Tinted windows are also a potential problem. The law requires that there must be a minimum of 75% light through the front windscreen and 70% light through the front side windows. Contravening this will get you a £50 non-endorsable Fixed Penalty Notice. A device is used to check the ratio of tint and can incur a £30 Fixed Penalty Notice.  Rear door windows and the rear window aren’t included so can be safely tinted.

The Road Vehicle Lighting Regulations (1989) state "except for emergency vehicles it is an offence to fit a blue warning beacon or special warning lamp or device resembling such whether working or not". 

Green lights can only be fitted on Medical Practitioners’ cars.  It is illegal to have a red light to the front of a vehicle or to have a white light to the rear unless reversing. This includes neon or LED lights fitted under or on the side of vehicles emitting a blue light. 

It is an offence to use fitted front and rear fog lights unless visibility is extremely poor. This is most common in conditions such as driving rain, fog, or snow. Fog lights should only be turned on when visibility is less than 100 metres.  Again, this incurs a £50 non-endorsable Fixed Penalty Notice. 

Number plates can also cause problems; you cannot misrepresent the characters in any way, shape or form. So be careful where you place screw covers so they don’t cover characters. 

Italic, bold and shadow fonts are all illegal.  Furthermore, the plate must be white reflective to the front and yellow reflective to the rear and the characters must be in black. There are very few exceptions to this. Failing to meet these guidelines can lead to a fine of £100 and removal of the number plate by the DVLA.

Fitting stretch tyres is becoming more popular and is illegal since it can affect the handling of the vehicle and contravenes the vehicle’s Type Approval. Three penalty points on your licence, a £100 fine or even court are possible if you get prosecuted under Sec 40A of the Road Traffic Act (1988) for fitting stretch tyres. 

Undercar lighting, particularly neon, is a troublesome modification as well. Red, green and blue are not allowed. It's also illegal if you can see the actual lighting tubes.

It's important to remember, though, that under car lighting is considered illegal if it is a distraction to you or other drivers. This is quite subjective, so be prepared for a police officer to ask you to switch them off immediately.

What’s legal:

You can still have plenty of fun when modifying your vehicle. For example, fitting an F1 style steering wheel is legal and encouraged if you plan to do any track racing in your vehicle.

Filters, turbos, and steel cat back exhausts are allowed but the car must pass an MOT emission test. 

There are plenty more legal modifications if you want to make your car more suitable for track-days or racing. Switching your seats to more supportive, "bucket" racing seats is allowed and suspension can be lowered as long as it doesn't compromise the springs.

You can also install bigger and wider alloy wheels, as long as they don't come into contact with the wheel arch.

Ultimately, before committing to any modifications, we recommend that you follow this three-step process:

Step 1: Check that your desired modifications are acceptable under the Road Traffic Act

Step 2: Ensure that the mechanic carrying out the modifications is fully trained in installing modifications for that particular make and model.

Step 3: Inform your insurance company of your new modifications. Failure to do so could invalidate your policy or seriously harm any future claim you would make. (Be aware that most insurers will increase your premiums, or even refuse cover when cars are modified).

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