This thread it fairly typical of TP. There is a serious problem in cities. Someone is trying to do something about it. And along come those who just don't 'get it'. Who feel they are the victim, by being asked to limit their contribution to pushing the pollution levels to way over the legal limits. And demand that they can continue to carry on polluting with their precious car that they lovingly chose. And demonstrating that they don't care about those suffering from their pollution. Some might even go as far as to 'deny' the pollution or the suffering. With claims that it's evil people out for political or financial gain.
And they write it all down in the posts for us all to read as 'evidence' of their arrogance, or lack of understanding. They clearly don't realise how bad they look.
And there are some (and I'm not pointing fingers at anyone) that don't seem to have any real knowledge in this area, that just keep recycling the rhetoric being pedalled by politicians, activists and the media, and making snide remarks.
Air quality is without doubt a serious problem in cities and road transport emissions apparently/unsurprisingly make a considerable contribution to this.
Society is MASSIVELY invested in Diesel engine technology. Current diesels are hugely cleaner than previous generations. Taking the older generation trucks, vans and cars (diesel and gasoline) off the road or at least out of cities is likely to help improve urban air quality. Getting shot of old vehicles is an easy target and almost a no-brainer. Problem is there is an awful lot of them and many people cannot afford to buy newer low emissions vehicles and are either unable or unwilling (perhaps both) to effectively scrap their car because it's good for the environment to do so.
Modern gasoline engines are mostly direct injection and produce similar amounts of particulate (number) as diesel. Gasoline engines appear cleaner because the particles are too small to reflect visible light, unlike particulates from older diesels which are larger and therefore more visible. Modern DPF equipped diesels release less particulates overall, but very much less visible particluates. Lots of very small particles are not good, hence the new emissions standards have a particle number limit for both diesel and gasoline vehicles.
There are no 'real world' legal limits for vehicle emissions, they are only required to pass a very specific (unrepresentative) test protocol.
EV, HEV, PHEV etc. are all interesting, but each bring issues that need to be resolved and again their emissions performance is regulated and tested using specific test methodologies. There are no real world emissions limits for these either. The test protocols may have changed since I was last involved in this four or five years ago.
The whole area of emissions testing needs revising and this is in progress, but that doesn't address the vehicles that are already on the road
Big politics is definitely in play in this area, one only has to consider who gains and who loses when new technologies are developed and introduced.
FWIW my/our current cars are both diesel:
One is a 2010 Euro 5 hatchback, equipped with an oxidation catalyst and particulate trap (DPF). It doesn't have a de-NOx after-treatment system, so tailpipe NOx emissions are basically the same as engine-out. These are minimised using a cooled exhaust gas recirculation (EGR) system, which works well enough to meet the Euro 5 test limits, but unlikely to be effective over the full operating range of the engine (which isn't tested under the regulations). In addition, increasing EGR reduces the formation of NOx, but it also reduces engine efficiency increasing fuel consumption and CO2 emissions.
The second is 2016 Euro 6 estate. It has an oxidation catalyst, DPF, EGR and a selective catalytic reduction (SCR) de-NOx after-treatment system. It presumably meets the Euro 6 limits during the test and I would expect it to have low emissions in real world usage. Though in practice NOx is still likely to be higher than the official test limit. BTW I wouldn't be surprised if gasoline cars exceed the test limits when driven on the road.
Anyway, in my view there is no panacea and this issue is going to rumble on for some time to come.
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