My 12yo car's ok, but I'm lucky (for now) as it's a EU4 petrol. Obviously other cities wanting this sort of thing may choose more or less restrictive criteria, though they normally follow what the most major one does.

One thing to bear in mind is that it is incorrect, as some people believe, that modifying a car to reduce its emissions to below the threshold means that they can now be exempt from such rules - they can't, as the rules apply to how the model, not the car, was tested before first coming to the EU market.

On the other hand, people removing DPFs, CATs and other OEM emissions reducing equipment fitted in accordance with the law will be breaking the law in some manner - not sure if it's just an automatic MOT fail or more than this, but I suspect a car that may have passed the ULEZ checker based on its OEM configuration would certainly not if the CAT and/or the DPF were removed, and if caught, would possibly be prosecuted even if the work had been done after it's last MOT.

When I saw the thread title I thought that ORB had unearthed one of those kit-car specials of the 50s and 60s - the Ulez Checker.

There was quite a spate of them - for some reason they all seemed to use the doors from the Austin-Healey Sprite, and the older ones were powered, improbably, by that desperate old side-valve Ford 1172cc engine that couldn't pull the skin off a rice pudding. I suppose parts for it were plentiful and cheap.

Seems like they are not set up correctly. ULEZ correctly identifies a 2005 Golf Mk5 as being exempt as it is a Euro 4 vehicle. However T-Charge seem to think it is not meeting the standards (even though ULEZ is s'posed to be more stringent). Go figure!