Slough business Onyx Performance has been convicted for failing to show that a vehicle it modified would not be used on a public road.    

The case heard at Reading Magistrates’ Court on 19 February was brought by the Driver and Vehicle Standards Agency (DVSA) following an investigation by its Market Surveillance Unit and is the second case of its kind in recent months, following the conviction of AET Motorsport for a similar offence in November. 

The court heard that despite disclosing that the planned modifications may lead to their client’s vehicle becoming unroadworthy, Onyx Performance still provided a ‘pop and bang’ service without establishing whether the vehicle would be used on the road. 

Crucially, the court ruled there is a heavy burden on companies that modify vehicles in this way, to satisfy themselves that cars are not being used on public roads. A customer should be able to show how they plan to move a vehicle once it has been modified.  

Roads minister Guy Opperman said: “It’s great to see DVSA cracking down on this anti-social and dangerous behaviour and successfully prosecuting companies who breach the rules. 

 “Everyone knows that horrific sound, when exhausts go “pop and bang” in the street, and cracking down on companies that fit these modifications shows our commitment to ensuring Britain’s roads remain among the safest in the world.” 

Chris Dormand, DVSA’s head of the Market Surveillance Unit, said: “Companies must satisfy themselves they are certain that vehicles which have had modifications designed for off-road use are not used on public roads.  Modifications designed for off-road use are illegal on our roads and businesses will be held accountable.   

“It is illegal to drive a vehicle on the road after the exhaust system has been altered to increase noise levels or adversely affect emissions. They are anti-social, unhealthy and result in an MOT failure. DVSA takes this activity seriously and where appropriate, we will prosecute companies who offer similar services.” 

When making modifications designed for off-road use, businesses must carry out adequate checks to make sure the vehicles they modify will not be used on the road. 

The ‘pop and bang’ service involved removing the catalytic converter and exhaust silencer, both legally required on a petrol vehicle. Vehicles modified in this way can only be used where it is legally permissible, such as private property or for permanent export outside the EU.  

DVSA analysed the vehicle for noise levels at a government testing facility, both before and after the modifications to determine the different outputs of the vehicle. 

Furthermore, removing the cat from a vehicle causes dangerous emissions to be released into the atmosphere, and removing the silencer means the legal limit for noise levels is likely to be exceeded. 

The judge hearing the case explained that if businesses make modifications designed for off-road use, they must make take all reasonable steps to make this clear to their customers and to also satisfy themselves that the vehicle is not to be used on public roads. Vehicles need to leave their premises on a trailer if changes made render the vehicle illegal for road use.  

Onyx Performance was convicted and ordered to pay a total of £5,800 in fines, victim surcharge and costs for fitting an unsuitable vehicle part to a vehicle which would make it illegal to be used on the road.