Minor nitpick, but tailpipes aren't the primary source of emissions. The study is about PM2.5[0]. which will chiefly be tires and brake pads. Modern gasoline engines are relatively clean, outside of CO2, though diesel engines spit out a bunch of bad stuff.
Exactly. The noxious tailpipe emissions in a city are usually from diesel trucks, small vehicles like motorcycles (small or absent catalytic converters), modified vehicles (catalytic converter removed or diesel reprogrammed to smoke), but not modern gasoline ICE vehicles.
The love for diesel engines in many European countries was always confusing to me.
PM2.5 is also a broad category of particulates that come from many sources. The PM2.5 levels in the air depend on many sources, with wind being a major factor in changing PM2.5 levels. It’s hard to draw conclusions when a number depends on the weather and a lot of other inputs.
Europe began embracing diesels 40yr ago when they were noisy and stinky and they did it because they taxed the crap out of fuel so people rightfully prioritized buying vehicles that got better fuel economy.
Giving a crap about CO2 is a recent thing.
In the US, Federal lawmakers would be voted out of office (even now after the science of climate change has settled) if they imposed taxes on fuels anywhere near as high as European lawmakers do.
Energy security. They didn't have north sea oil back then. Buying from Russia or the ME was fraught with political peril. And of course the .gov is never gonna pass up a chance to increase revenue.
[1] https://www.gov.uk/vehicle-tax-rate-tables/rates-for-cars-re...