Banned Car Modifications

If you drive a modified or classic car, you’ve probably heard about last year’s proposed EU shake-up of MOT regulations, which would have made many car modifications illegal on British roads. Under the proposed new rules, all vehicles would have to remain identical to the specification they were in when they left the factory, meaning that any modifications, from new windscreen wiper blades to bigger exhausts, would automatically lead to an MOT failure.

The implications of the proposal were even more daunting for classic car owners, since in many cases, original parts for their vehicles are simply no longer available, so non-original parts are used out of necessity. The ruling would have meant that thousands of classic cars in the UK would have become automatically illegal. Thankfully, these proposals have now been rejected, but it got us thinking, what car modifications are legal and illegal on UK roads?

The laws surrounding car modifications are rather unclear and always subject to change, so whilst we can’t guarantee the up-to-date accuracy of this information, here are a few general guidelines you can follow when modifying your car;


Neon light modificationsare legal if you can only see the glow, but no visible or distracting bulbs should be visible, and you should be able to turn them off if the police ask you to. The standard lightsat the front and rear of the vehicle must always conform to legal requirements, with two white or yellow at the front, two red at the back, and orange indicator lights at the front, rear and both sides.

Window tints
are legal to any extent at the rear of the vehicle, but the windscreen and driver’s/passenger side windows must not be tinted to the extent that visibility is impaired. Legally, this has been interpreted to mean that a minimum of 70% of visible light must be transmittable through the side windows, ad 75% through the windscreen.

tend to be an area of confusion. Whilst it is not illegal to sell large or big bore exhausts, it is an offence to fit the vast majority of them to your vehicle and drive on a public road. Usually fitted to increase the sounds emitted, they often contravene the type approval of the vehicle, which is an offence. There is no legal requirement for police to measure the sound emitted from an exhaust, only an opinion that it is not standard and is noisier than a standard vehicle of the same specification. This includes removal of exhaust silencers. The fact that modified exhausts can pass an MOT is irrelevant, as MOT’s only test for exhaust gasses and emissions, not noise levels.

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In car entertainment
moving images, such as DVD players and games, are illegal to place in the view or a driver, but acceptable elsewhere in the vehicle.

Wheels and tyres
modifications to these can alter your cars behaviour on the road, so it’s recommended that you only fit wheels and tyres which are approved by the car manufacturer. You should ensure that there is adequate clearance between the tyre and the body of the car to allow suspension movement.

modifications to your cars suspension can be dangerous and can affect its stability and handling capability. Whilst not illegal, all suspension modifications should only be carried out by a competent engineer.

are a legal modification to your car, so long as they do not have any sharp edges, hinder your driving visibility, or pose any risk of coming detached whilst driving.

Number plates
must comply with current British standard legislation, without exception, meaning that they must be displayed in a prominent position, un-obscured, and without any misleading character configuration.

In any case, it’s important that you fully investigate the legality of any modifications you plan on making to your car before implementing them, and fully disclose any changes to your insurer. Most car insurance companies in the UK will rate on modifications made to your vehicle, and may charge additional premiums, or refuse to pay out on a claim, if undisclosed modifications are discovered during the policy term.

Car insurance from car insurance companies in the UK is expensive enough without being charged additional premiums, or facing a hefty fine for illegal modifications, so for more information, we recommend you contact the DVLA for more specific and up-to-date rules.

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