> Generally the rules are stronger and the enforcement is weaker (because turning the screws on the poors over a check engine light isn't as tractable for us as it is for Europe, generally speaking).
To be fair the amount of Diesel cars on the road in the EU with abhorrently poor emission systems is shocking; I was at VW during dieselgate, and worked with Bosch and VW during the buy-back program and VW are by far the only violators in the EU and in the periphery countries for lacking emission standards.
I was behind mid 2010s diesel Opel for ~35km on my way to Slovenia and I have been in enclosed green houses with diesel tractors so I'm pretty sensitive to it, and it was so absurd that such a thing was allowed on the road.
Typical check engine light failures (P14X/0420) are susceptible to modifications to pass if you know what you are doing, visual inspection isn't always as stringent as you'd think even with the STAR test sites in CA, which has the strictest emission laws in the World. When I was in motorsports we had a series of people we could rely on to pass our respective track-built machines on the road, but ultimately you realize that it's not worth the time, resources or risk and that the car (if properly built) no longer belongs on the road anyway.
As an environmentalist who has struggled with addictions to 'car-caine' I've since downsized from a revolving inventory of 5-6 cars, and 3 motorcycles to one of each: what I think is even tougher is to actually make sensible policy and regulation regarding them without it being simply a way induce needless consumption.
Case in point is the absurd World of the 2-3rd Gen Prius used car market and the catalytic converters, which has always had a lot of theft since it was released but have reached an Worldwide [0] extreme this year due to the astronomical rise in PM prices for those metals (inflationary pressure more than demand) so coupled with the supply chain shortages from Toyota and the rise in sudden demand many cars which were in compliance and within emission specs were simply scrapped because when Toyota couldn't deliver there was no other certified manufacturer for the part and something as simple not having a Toyota stamp was an automatic failure.
Even though some owners reported emission testing within spec of counties within WA or OR which have less stringent standards than CA but still worth noting their compliance. Their insurance policies payout wouldn't cover a similar ranged car purchase and the only alternative was to sell it out of state and use that sum (usually half the cost of properly registered Prius in CA) and to buy another used one.
0: https://www.hotcars.com/heres-why-prius-catalytic-converter-...