Is it the vehicle manufacturers, or people buying cars and vans without thinking? The ABD has recently issued a press release on this topic which lays the blame firmly on Government. See http://www.abd.org.uk/government-entirely-responsible-for-urban-vehicle-emissions-issues/ . In London that means the Mayor of London supported by TfL, plus the local London boroughs.
In summary vehicle emissions have improved enormously in the last few years, but those improvements have been defeated by unwise policies for tackling traffic congestion. Traffic speeds have slowed, which increases pollution. The ABD suggests in our press release how pollution could be tackled with more sensible policies.
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