We all know how to reduce air pollution in London caused
by road vehicles. We've been through this several times
before in other threads. Vehicles have not suddenly become
more polluting in the past twenty years. They have become
cleaner. The huge increase in air pollution in London is because
the roads have been changed. (TfL calls them "improvements"
I call it sabotage) Vehicle journeys take far longer, their engines
are running longer; hence an increase in vehicle emissions.

There is also the issue of 20mph zones. Vehicle emit more
pollutants at 20mph than at 30 mph.