Department for Transport puts record straight on modifications to vehicle emissions

Mechanics that modify a vehicle in such a way that it no longer complies with regs could face unlimited fines

Department for Transport puts record straight on modifications to vehicle emissions
While some modifications may be purely cosmetic, the DfT say some modifications can result in legal, safety and health implications.

The Department for Transport (DfT) has published new guidance covering the legal, safety and health implications when it comes to modifying vehicle emissions.

The guidance encourages vehicle owners to seek professional advice from mechanics to ensure that any vehicle modifications are safe and within the law.

The DfT said: “It is not always obvious to vehicle owners that some modifications will make the vehicle illegal to use on the road, irrespective of whether the insurer is prepared to provide cover.

Exceeding type approval limits

“For example, removing a catalytic converter or diesel particulate filter will almost certainly result in a vehicle’s emissions exceeding type approval limits and make the vehicle illegal to drive on the road.

“Engine re-mapping may also result in non-compliant emissions.

“It is the driver who is responsible for ensuring compliance.”


Under the Road Vehicles (Construction and Use) Regulations (Regulations 61(7) and 61A(3)) and the Road Traffic Act 1998 (Section 42) it is an offence to use on a road a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet.

The potential penalties are £1,000 for a car and £2,500 for a van, lorry or bus.

Under the Road Traffic Act 1988 (Section 75) it is an offence to alter a vehicle in such a way that the use of the vehicle on a road would be unlawful.

A person altering the vehicle may be found guilty of an offence under the Act and the potential penalties are unlimited fines.

“Potential to kill”

The DfT adds: “A badly modified vehicle has the potential to kill its occupants and pollute the air.

“Making changes to the engine management system in an attempt to increase performance, coupled with the removal of all or part of the emissions control system, may lead to significantly higher levels of harmful exhaust emissions which can then find their way into the vehicle’s interior.

“Incorrectly fitted parts or unapproved changes to a vehicle can lead to a potentially deadly outcome for vehicle occupants.”

Do you have any concerns about vehicle modifications? Share your comments below.

Home Page Forums Department for Transport puts record straight on modifications to vehicle emissions

This topic contains 2 replies, has 2 voices, and was last updated by  Alan 10 months, 4 weeks ago.

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  • #153099 Reply

    Gary Burgess MIMI

    My personal view is that it will not alter the already status quo: that is vehicles have been modified from the manufacturers original design for years. This country like many make laws that ‘have no teeth’. As far as the MOT is concerned: the emissions test for diesel vehicles has been s farce for years. We cannot even enforce legislation that is current today.
    Just ministers attempting to keep the green lobby quiet and place a band aid over a failing emissions legislation.
    As an industry why can we not accept that the repair of vehicles is our lifeblood therefore fix the problem rather than circumvent it. After all it is not our problem it is the customers.

    #153112 Reply


    What about those ridiculous stretched tyres? Rear wheels with massive amounts of camber? Plenty of other unsafe stuff going on (just look on social media to see the amount of young drivers cutting suspension springs to lower their cars). Remapping if done correctly can actually improve emissions in certain cases, as they manufacturers use a “best case” map when they build the cars, ones that work for mass production. Correct mapping improves on that, as it is tuned specifically to the car. Obviously removing catalysts and DPF’s is a no go due to legislation, although there are options for using sport cats or high flow units.

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