The Department for Transport is consulting on changing the law that governs emissions from vehicles already on the road. It closes at 11:59pm on Sunday 6 September 2026, so if you want to say anything, this week is the week.
I have read the whole thing and responded. What follows is what it actually says, rather than what the internet has decided it says, because the two are some distance apart.
What is actually being proposed
At the moment there is a gap. New vehicles have to meet the Euro standard in force when they are built and registered. Once they are on the road, the rules that keep them at that standard, in regulation 61A of the Road Vehicles (Construction and Use) Regulations 1986, were only ever updated as far as Euro 4 and Euro V. Anything built to Euro 5, Euro 6 or Euro VI has no ongoing legal requirement to keep its emissions control system working.
DfT wants to close that gap by requiring vehicles to keep meeting the standard they were built to, for life. Enforcement would run through existing sections of the Road Traffic Act 1988, section 42 for using a non compliant vehicle, section 75 for alterations to vehicles, and section 76 for fitting or supplying unsuitable parts. Penalties on conviction in the magistrates’ court run from £1,000 to unlimited fines. DVSA would enforce.
The evidence base is worth reading rather than dismissing. A roadside remote sensing study of over 94,000 vehicles across several UK cities found that fewer than one in ten passenger cars met the official nitrogen oxide limits, and that roughly two thirds of Euro 5 and Euro 6 diesel cars were emitting more than three times the level allowed. DVSA’s market surveillance unit logged 331 intelligence reports relating to emissions modifications in 2024, and DfT suspects that is a small fraction of the actual activity.
Which vehicles it applies to
This is the part most people have got wrong, and it matters.
Regulation 61A applies to vehicles first used on or after 1 January 2001. The proposal extends the standards it covers, up to Euro 6 and Euro VI, rather than extending the date backwards. On the most natural reading, a 1997 Supra, a 1999 R34 or anything else registered before 2001 sits outside this entirely. My R35 is squarely inside it. So is every 2001 onwards project.
I say most natural reading because the operative sentence in the consultation refers to all road vehicles in-use in GB from 1 January 2001, which is not the same test as first used on or after that date. Those two phrasings produce very different scopes, and the second would pull pre 2001 cars into the regime for the first time. That is one of the things I have asked DfT to nail down.
Motorcycles are a separate issue. Regulation 61A has never applied to category L vehicles. DfT proposes to include them, while stating in the same section that it has limited analytical evidence specific to in-use emissions from motorcycles and could not identify a clear reason to exclude them. Extending a criminal prohibition to a whole vehicle category because no argument against it was found is the wrong way round.
The four modifications DfT says are always illegal
- Removal or deletion of diesel particulate filters, or gasoline particulate filters on petrol vehicles
- Removal of three way catalysts, often accompanied by alteration or removal of sensors and sometimes ECU remapping
- Manipulation of SCR and diesel exhaust fluid systems, the AdBlue delete
- Manipulation of EGR systems, whether physically or by remapping
DfT is explicit that it is not trying to ban modification generally. The document says vehicle alteration is a legitimate practice embraced by tuners, repairers and enthusiasts worldwide, and that it is not seeking to stop people fitting generic rather than OEM parts. It also says that the legality of a modification, hardware or software, depends primarily on how it affects the standard the vehicle was legally built to.
That is an outcome based test, and I have no argument with it. If the car meets its limits, it meets its limits.
Where the drafting contradicts itself
The consultation asks whether a modification should be unlawful where it is a known and proven fact that it will always result in illegal levels of emissions. The word doing the work there is always.
Three of the four items survive that test. SCR, DEF and EGR systems are manipulated in order to defeat them, not to replace them. Delete a DPF and you have deleted a DPF.
The catalyst item does not survive it. Removal of three way catalysts describes a physical act, not an emissions outcome. It catches deleting a cat and running nothing, which should absolutely be illegal. It equally catches replacing a failed or obsolete original cat with a modern aftermarket one, which is ordinary repair, and which on a properly calibrated closed loop setup routinely meets or beats the original. That is not a case where illegal emissions always result. It is a case where they do not result at all.
The fix costs DfT nothing. Describe the harm rather than the component: removal of a three way catalyst without replacement by a catalytic converter that maintains the emissions limits applicable to the vehicle. Deletion stays illegal. Repair stays legal. The same wording change applies to the DPF and GPF item.
The durability problem
This one is on the face of the consultation, and I think it is the strongest objection available.
Manufacturers have to demonstrate that their emissions technology performs as expected for 100,000 km or five years, whichever comes sooner. Separate pollution control devices, catalytic converters among them, have to last 160,000 km.
The proposal puts an obligation on owners with no durability ceiling at all. An owner would carry indefinitely a standard the manufacturer only ever had to guarantee to a defined limit. A 2003 car on 180,000 miles with an original catalyst that has simply aged is not a vehicle anybody modified. It is a vehicle that got old, which is what vehicles do.
What the consultation does not answer
- There is no mechanism by which you can establish that you are compliant. No certificate, no list of authorised testing bodies, no independent appeals route. The proposal creates an offence without creating a way to prove you are not committing it.
- Alternative fuels are not mentioned anywhere. If a car is converted to E85, is compliance demonstrated on E85 or on the fuel it originally ran? How is a flex fuel car assessed when ethanol content changes between fills? Nothing.
- The legal weight of an MOT emissions pass is not addressed. DfT acknowledges the annual roadworthiness check is limited in what it can assess, which leaves owners relying on a test that may not be the test.
- Burden of proof is not stated. Does DVSA have to establish the standard applicable to your specific vehicle and then prove it exceeds that, or is the presence of aftermarket parts enough to start the argument?
This lands on the industry before it lands on owners
DfT says enforcement will likely focus upstream, on the practices behind illegal modifications, because roadside and annual testing can only assess so much. Read that properly. The people most exposed are not individual owners with modified cars. They are mapping outfits, exhaust fabricators, remap resellers and workshops, who under section 76 can be prosecuted for fitting or supplying unsuitable parts.
Which is exactly why the missing compliance mechanism matters. If a business is expected to know whether a configuration is legal before it hands the keys back, somebody has to define the test it applies.
How to respond
The quickest route is the online response form, which lets you save and come back to it. You can also email your response to ivs.consult@dft.gov.uk. The full consultation document is here. It closes at 11:59pm on Sunday 6 September 2026.
If you do respond, answer the questions they actually asked. The consultation has a defined question set and responses get coded against it. A long free text essay that does not map to those questions is much easier to summarise into nothing. I know this because I sent the essay first.
The points I would make, if you want somewhere to start:
- Agree that a modification which always produces illegal emissions should be unlawful, then object that catalyst replacement does not meet that test and the wording should describe the outcome rather than the component
- Ask for the durability obligation on owners to be reconciled with the 100,000 km and 160,000 km limits placed on manufacturers
- Ask for a compliance certification route and an appeals process to exist before enforcement begins
- Ask for the 1 January 2001 scope to be stated unambiguously on the face of the instrument
- Say the six month lead-in should be longer, and should start from publication of final technical guidance rather than from the date the legislation passes
Where I have landed
I am not against this. Deleting a cat or a DPF to make a car louder or cheaper to run puts pollution into air that other people breathe, and I do not have a defence for it. The remote sensing numbers are not invented.
My problem is narrower than that. As drafted, one line of this treats replacing a worn out component with a better one exactly the same as removing it and running nothing. That is not an emissions policy, it is a parts policy, and it will not clean up a single mile of air.
I would like to hear from anyone who runs a business doing this work, because you are the ones who need certainty out of it and you are the ones the enforcement is pointed at. Comments are open.
