I've said this in various places already, but I'm VERY surprised that diesel vehicle pollution hasn't been cracked down on yet. It was dealt with on petrol vehicles some 25 years ago but yet even brand new diesels seem to chuff out clouds of soot on acceleration.
A poorly maintained car without a DPF might do, most don't.

Suggesting there is room for improvement that doesn't involve punishing car drivers is heresy. Next you'll be suggesting that speed bumps, traffic islands next to bus stops and all the mostly empty buses driving around aren't actually helping to reduce congestion an pollution.
